This reminds me of what happened to Alaba at Bayern Munich. Van Gaal promoted him to the first team, but he more or less stopped playing him after a
mediocre game against Frankfurt. He struggled for minutes in the following season and was loaned out. Januzaj has had many more chances than Alaba, but he had the luxury of playing in the Premier League before Van Gaal arrived so that probably helped him.
I think Van Gaal rates Januzaj, but he was probably on the fence regarding how much of an impact he can have on the first team hence he gave him a few games to assess his value. I don't think he did too badly and being an impact player off the bench is what he should have been for us this season, but a move to Borussia Dortmund is great for his education. He'll be training under a different regime, one that suits his direct style IMO. He'll hopefully improve his ball retention skills (which he's actually been better at compared to his last two seasons), how to move off the ball, and positional discipline, all of which are severely lacking. Plus he's going to be working with Reus, Mkhitaryan, and Kagawa. FWIW, all three have been excellent this season.
Tuchel wanted a different player on the right, specifically a left footer. He couldn't get Yarmolenko, so he went for Januzaj, who is an unpolished talent but saves you the hassle of panic buying. No one knows how much playing time he'll get a Dortmund, but I think he's going to surprise many people with his performances.
Well, the Alaba loan to Hoffenheim for half a season was certainly a well executed action to develop the Austrian. He was already strong enough to improve the first team of Hoffenheim and his sheer versatility in terms of positions (LB/LW/CM/DM) allowed him to play pretty much all the availabe game time.
I don´t see the similarity to this deal, though. Januzaj is like Alaba back then in the middle of his development and while he technically went into his third EPL season, in actual game time he has only one full season under his belt. He is still fairly raw and probably just at the beginning of his development curve. Logically he should be treated as the talent he is and that is often not possible for ambitious clubs who want to win titles, so they loan out or sell players with rebuy clauses. A loan deal in itself is understandable, albeit surprising because no player for his position came in which stretches United pretty thin there.
As destination they chose us and I read a lot of posters being very happy about that choice. "Better than to send him to Sunderland" was probably my favourite so far. They refer to our style or culture of play, our pretty highly rated coach, the atmosphere, the quality of his team mates and so on. I mean, I´ll take all the compliments I can get about my club, but what they don´t take into account are the circumstances of this deal.
In general, clubs which loan for such short amounts of time (half - full season) without buy clauses do not care about the development of the players. They don´t benefit from developing them, because the time frames are way too short to get anything meaningful out of this. We are the same. We don´t loan Januzaj, because we want to help United or Januzaj on his way to a top class player. We loan him to have a player who performs under certain circumstances, in his case to rest starters, to replace them if they are injured and as impact sub. Him being a left footer might help him in a few situations to get the edge over Hofmann, but it won´t bring him into the starting XI without injuries of the starters. All three of our first choice offensive midfielder are both footed, so no need there.
The problem with us seeing him as a squad player instead of a talent is, that there will be no compromises because of the promise of future performances. All that counts are the current performances, no easing into a new league or more freedom to make mistakes as talents should have. He either hits the ground running for us and uses the few chances he will get to impress or falls in the internal ranking rather quickly.
There are also other dangers for Januzaj here. If we indeed loan him without a realistic option to keep him longer, it simply means that we did not get one of the permanent solutions we wanted. Nobody knows if these options become available in the Winter window, though. Worst case scenario for Januzaj would probably be if someone like Yarmolenko decides to sign for us then and takes up all the game time which he would have gotten. There is no cost in sending the Belgian to the stands for us, because United was kind enough to loan him to us without a fee (some reports even state United still pays half his salary). Similar to that would it be if one of our highly talented academy talents, who currently train under Tuchel, catches the coaches eye and he sees room to give him a first taste of first team football in front of 80.000 people. You can bet that he rather gives him minutes than some Belgian kid who is gone in the Summer.
No matter what details this loan deal include, one thing for me is pretty certain. Van Gaal had no problem to screw over Januzaj here. He either gave him up alltogether or send him to a club, where it will be harder to succeed than at home. This in itself contradicts what a loan move should be about. Mourinho got a lot of (deserved) flak on here for his dealing with De Bruyne, but he had at least the sense to send him to Bremen, where he was welcomed with open arms and even some stupid interviews would not stop them from fielding him every week, because it was bloody obvious he was their best offensive player. He benefited a lot from his first season in Germany.
For Januzaj on the other hand, there will be a pretty high chance that he will look back to his season at Dortmund in a year and see a wasted one. He might have picked up a few things in training, but nothing, absolutely nothing beats consistent game time at the stage of his development.