You're so adamant about it because the memories you have of attractive football are associated with a period of dominance in the Premier League (United in Europe is a different story). If that wasn't the case, you'd probably think a bit differently. You believe that these two always go hand in hand and that if we start turning every game into an end to end contest, we'll eventually enter another era of dominance in English football. The truth of it is that the club that "leads the line" by playing expansive football is almost always the one that has the best players and the best creative/attacking options. We spent a good quarter of the century trying to play entertaining football while our arch rivals were making a name for themselves as the "best team in the world" with Hansen playing backpasses to Clemence and Grobbelaar. Thank God there weren't internet forums back then.
If you're not that club (and we clearly aren't at the moment), you try to make the best of what you have to work with. If this set of players was good enough to play on the front foot, they would have done it under LvG. There's a reason why most renown managers turned down the job when it was offered to them (according to SAF himself). Think about it a bit, there's a lot of work to be done here. One of my favorite sides in the history of football, AC Milan, steamrolled the Serie A in 92/93 and reached the EC final with their magnificent Dutch trio. When they lost them in the following season (especially Gullit and the injured van Basten) they won the league by scoring 36 goals in 34 games and they went all the way in Europe. Capello managed them in the best possible way in order for the team, the best team in the world at that time, to meet the standards that were set for them.
United can't afford to have one of the best attacks in the league and one of the worst defenses. You're basically asking for a season similar to the one the two Merseyside side clubs had in 15/16. You may say that you might be ok with it but Niall would probably have to lock this place down for a couple of hours after each of our games. And the best talents in the world want to be in the place where the trophies will have better chances of going. That's why Bayern, Juventus and PSG are draining their rivals of all the native talent.
We showed more patience with LvG than any other fanbase would have, we can at least offer the same thing to Mourinho. Let's see how we'll end this season. We say we want a team for the future and we have assembled some very promising players in Lukaku-Rash-Tony-Pogba-Bailly and others (even Lindelof shouldn't be written off) but they need more time to develop. We could have splashed money at the likes of Lewandowski-Hummels-Bale-Neymar etc. and we would probably have a much better team by now. We've chosen a different path.
And stop looking at what Pep does, seriously. The man is a one-off, the only manager in the world of football right now who can assemble a starting xi with 7 or 8 creative players in it (the FBs, the three up-front, the seemingly extra-light midfield and one of the CBs) and challenge for every big prize that's there to win. There's no one else out there who can create a team whose focus will be to be the greatest creative force in the league while also being one of the best defensive units (via pressing and possession). He did it last season too when this forum was laughing at him, his side created the best chances, quality wise, and the defensive setup let little gaps for exploitation (again quality wise). It was the comical individual errors that cost them a better finish and now that these are minimized, we see how strong they are. The other three best sides in the league, Chelsea-Tottenham and United, all depend, more or less, on solid defensive performances to win football matches. Given the fact that Chelsea have a team set in the last decade to excel in this type of football and that Spurs are blessed with some exceptional talents and have Poch for quite some time at the helm, these two teams look more fluid than us atm. But we're not far behind them.