That's not true at all. There's stats that have been posted ad infinitum through this thread showing that his chance conversion rate (when played centrally) last season was better than any other striker in our squad. There's no chance this was true a few years back, so that's clearly an aspect of his game which has improved.
I also disagree that the Chelsea model is somehow radically different from ours, with better outcomes. Both clubs loan out players to develop them. If anything, United have a better record with a much higher number of players that have been sent out on loan, then come back to make a useful contribution to winning trophies. Welbeck fell into this category, even though he has since left. Ditto Cleverley and Evans (not to mention former greats like David Beckham) Chelsea have singularly failed to match this right up until this season, with Courtois and Lukaku, both of whom seem to be really exceptional talents. The risk of sending young players out on loan is that they will be marginalised by managers who would rather develop their own players or struggle to impose themselves at a club that is floundering. If the player concerned really is exceptionally advanced as a footballer for his age, then this is less of a risk. For relatively late developers like Danny they're no more likely to get the game time they need on loan than they would if they stayed put. Obviously, he seems to have turned the corner now and probably could have had a very succesful loan this season. It's quite possible that he would have, if the club wasn't intent on balancing the books and/or the player himself wasn't willing to go out on loan.
Last season there wasn't a large enough sample size to determine anything in terms of Danny Welbeck's productivity. He played centrally sporadically, often against weaker teams or at times coming off the bench against tired legs. To talk convincingly about his "improved productivity" he would have to score 15-20 goals in a season, something he has never done or looked capable of doing.
I agree that selecting the appropriate club is key to the development of a player and Chelsea got it spot on with Courtois/Lukaku. I think we've often overrated our players and sent them to clubs that are actually above their level, which defeats the purposse of course. Cleverley is another player who should have been sent out on loan for another 2 seasons. He was starting to look like a well rounded player until we prematurely dropped him into a poor midfield, whereby his confidence dropped (despite a few good performances) and now he's at Aston Villa. Jonny Evans who you mention is another player who is now 2-3 years behind development wise, because he had several seasons playing sporadically in his youth (although for a defender it is nowhere near as terminal).
I disagree re: Welbeck's playing time. It was clear at Sunderland that he was playing whenever he was fit, almost always in his preferred position. I said it at the time and I reiterate it now, he should have had another season there (as Bruce alluded to at the time). After this in my opinion he would have had his pick of loan clubs for a 3rd season whereby I'm sure a club like Everton would be offering a nice loan fee (they wouldn't pay a hefty loan fee without wanting him as their main man). Likewise Fergie should have sent him on loan when he signed RVP.
At United we seem to have this view that if a player can fractionally contribute to our season, we should keep them in the squad, as we benefit. Whereas we should look at what is best for the player's development long term. Once they have the feel of playing with great player's the likes of Januzaj and Wilson should be similarly treated. Unless they show signs of displacing great player's at a young age (ala Ronaldo).
By the same token then you might as well loan out or get rid of Januzaj & Wilson as well because they might cost you points. Fergie got your club to where it is by thinking long term not just taking the easy simple solution.
As above. Januzaj and Wilson should be given maybe 2 years with the first team where they can train with quality player's and immerse themselves in the United culture. If they are an exceptional talent they will force their way into the squad in their preferred position regardless. If they are a very promising talent but not quite at the level we require they should be loaned out.
With midfielders (and defenders somewhat) in my opinion they can be afforded more time as every single lapse of concentration will not necessarily cost you goals and consequently points. If Januzaj makes a bad decision he usually concedes possession in the middle of the park, if a centre forward or goalkeeper make a bad decision it is often goals not scored/goals conceded.
It's not an easy/simple solution to take long term gain over losing a decent squad option short term, quite the opposite.
No, your first goal should be getting back into the top 4 and this was made unnecessarily harder than it needs to be because you improved a rival´s side out of your own choice in an area where they needed it. People act like Welbeck had the power to force this move, when he still had two years left on contract and United sure as hell did not need the money. If Welbeck wants to leave, then you give him clear options: either a move abroad to a CL side or a transfer inside the PL to a club, which is not a direct rival. Out of all possible clubs you could have chosen, Arsenal was the worst option.
On one hand people argue, that you did not have the luxury to develop him further because of the possibility that it would lower your chances to qualify for the CL, but then you sell him to a direct rival, where he could effectively do the same by making Arsenal strong enough to stay above you and occupy a CL spot. Makes no sense.
Again that's your opinion. United's board won't be thinking top 4, they will be thinking how can we get back to winning titles. Arsenal are not a particular threat to United winning titles currently; City and Chelsea are.
Top 4 is small potato's for a club like United and Arsenal are have not been a "direct rival" since 2008.