Stam made his first competitive return to Old Trafford having won six trophies in three years as a centre-back between 1998 and 2001, but after an early reception from the home crowd which he deemed "marvellous" witnessed his side be outclassed by their Premier League opponents.
Wayne Rooney's record-equalling strike, in addition to Anthony Martial's effort and Marcus Rashford's brace, helped current FA Cup holders United to an eight successive win in all competitions as the Royals' wait for a first ever win at Old Trafford continues.
Yet despite the gulf in quality between United and Reading, Stam hailed what he felt was a learning curve for his squad - who currently sit third in the Sky Bet Championship in his first season at the club.
Stam lays gauntlet down to Reading players to learn from losing experience
The Dutchman told journalists afterwards: "I think it's a great experience. There's not always experience when you're winning games, but also when you're losing games.
"I think in the way that we think about football, where we are at the moment, starting from last couple of seasons being 17th and 19th in the league and now 3rd in the league, wanting to play a certain way of football and growing as a club and a group, a squad, and making progress - we've done well in the league.
"If you get the opportunity to play against a side like this, with the qualities that they have, they're in the top of the Premier League and are a top team in Europe as well, it's quite a big difference between the two teams.
"It's good for the players if you play against a side like this. You need to be aggressive, you need to be very sharp. You know how they're going to start the game.
"They've got the pace, the quality, if you give them time on the ball - especially the first 20 minutes, they had that - they make it very difficult and very hard for you. Of course I hate losing, even against a side like United.
"But the thing is what the players do with it. It's what the squad does with it, how you improve yourself to do better and make it harder for a team like this if you play against them.
"Hopefully, they'll take that. Every player in the Championship or wherever, they want to get to the level of this and playing against, or in, a team like this.
"Players need to learn from playing these games for what they need to progress in to become a better player and eventually get to the level where they are."
My team are working hard at what they need to, insists satisfied Stam
Stam also bemoaned that his side were not aggressive or concentrated enough defensively, conceding twice inside the first quarter-of-an-hour.
He lamented the absence of the "very important" Paul McShane, himself a former United player, in defence and added: "But it's not only up to one man. It's about how you perform and how you start a game like this.
"If you play against a side like this, you need to be very, very sharp, very aggressive, don't give them a lot of space. We spoke about that.
"In the beginning of the game, the first 20 minutes, we were a bit too easy-going. We could have done a little bit more. If you give them that time, they can punish you. That's what they've done.
"We did well in keeping possession at certain times but going forward, didn't create enough chances. But they were looking of course in case we lost it.
"If you lose it, if you play possession you're open and you leave big spaces, and then the first touch they had they were going forward. Especially with that third goal, they played Rashford in and he's away with his pace and they can punish you.
"You need to be in those moments. I've told it to the team as well, if you're against a side like this and attacking, you need to be very focused on the defensive part as well because if you lose it, they're gonna go forward and use their pace up front and the qualities they have. They can harm you, and that's what we've done.
"Certain players did well, very well. I can't blame my team in how they performed because normally, and today as well, they're working hard in what they need to do.
"The only thing is - what we need to do - to look at this game and how the opposition is playing and what they're bringing to the game.
"Also if you look at the quality they have, if you play a top side and they play against us, you could've thought maybe they'd slow it down but no, they kept on going.
"They want to bring everything and give everything to get a result. That's what you need to learn playing against a side with those players."
Becoming a manager isn't easy, even after a top-flight playing career, declares Dutchman
As well as it being a learning experience for his Reading players, Stam declared that he will take things away himself - his time at the Madejski Stadium representing his first job as manager.
He admitted: "I'm always learning. The thing for myself, as well, I need to learn because being a manager and being a player is a totally different job.
"A lot of people think that if you played at the top level, then it's easier for you to become a manager and do well. No, it's a totally different job.
"You need to learn and stand in front of a group telling the players what to do, telling the group what to do differently if it's difficult for yourself, and how you can improve. Even talking in front of a group is already different because you've never done it as a player.
"It sounds easy to become a manager at top level but it's not. You need to really get into it. You need to grow into it as a coach and a starting manager. Eventually, you're going to be deciding for yourself if you want to do that. If you want to make the decisions yourself, which I wanted to do.
"The thing for me that's important is if you like it and if it's going quite well. I've played at the top in Europe, so I know what to expect. I know what people or players need to do, need to bring to the game, to get to that level themselves or as a group.
"If you can translate that to your group, and hopefully they improve and individually get better, hopefully also as a team they get better, you'll get results.
"Until now, in the Championship we're doing quite okay, also compared to the budget we have compared to the budget of other teams and what they can spend.
"I'm happy with the attitude of the players we have, the atmosphere within the group and how they react to each other as well, and eventually by having everything together, you're going to have results.
"Of course for us to compete with the likes of United, it is very difficult. You can't do that. We need to be realistic in what we can bring to the game today as well."
Royals boss: We can approach rest of our Championship campaign with confidence
Stam hopes his side can now turn their attentions to promotion, with Reading currently six points - albeit with a game in hand - behind the automatic places.
He noted the disappointment of their FA Cup elimination and said: "I'd rather us go through in the FA Cup as well and have extra games, but every game - we take it as it comes along.
"Every game, we want to have a result. This game, we wanted to do well as well and hopefully get a result even though we knew it was going to be difficult.
"Now we're out, we need to focus on the league. We can do that again with confidence to do well towards the end of the season.
"It's not going to be easy in this league, even in the Championship, to win every game because there's a lot of competition there as well. We're going to give it a shot and we'll take it game to game."
Stam is expected to strengthen his squad with the £3.75 million addition of Liverpool outcast Tiago Ilori in the coming days, the Portuguese defender set to have a medical ahead of his proposed move.
But the manager refused to reveal anything on the deal for the 23-year-old, stating: "He's a player that's on our list, but I need to talk to [Director of Football] Brian Tevreden [to see] if it's going to happen or not."