Rashford is there for loan, not for permanent transfer, so Villa could use him for bench, nothing more. If anyone thinks that Rashford will be used as starter and will look to have a better result, you are kidding yourself, you are not going to see that and we will not have that.
The only reason Rashford was loaned out was the fact that he would be a decent bench player, and they are not entirely sold on the whole "he doesn't work" topic, so they wanted to probably watch and see if he is actually as lazy as Amorim says he is. If that is the case, then it's a loan and he will go back, if it is not and he looks great then they could just buy him out if they want to, or even if not then they will just have a working Rashford for a few months that will help him.
Rashford did go to a "better" club in the sense that Villa is at UCL, so it's a good thing for him, but it's also a huge risk. Now he has to show himself, he is kicked out of his own team ,for being lazy, he has to prove everyone wrong, or he is going to prove them right.
This option also seems to be Barcelona's move to borrow Rashford, by joining Hansi Flick's squad, he will be useful as a substitute player or maybe a main starter in certain cases. Unfortunately, Barcelona is constrained by financial problems. Aston Villa borrowed Marcus Rashford, besides Asenssio and Axel Disasi for the needs of his team. Well, it doesn't mean that with Rashford joining he will become a core player in Unay Emery's squad, therefore he must prove his capacity. In the contract between Manchester United and Aston Villa there is an option to buy Rashford for £ 40 million if they are impressed with his loan period. If what happens is as you say, it means that Marcus Rasford consciously let his career be destroyed. Rashford seems to have a problem that disagrees with several previous United coaches, which in the end he tends to not have the spirit to fight and work hard. This attitude is his homework for him to fix, because the problem will be serious if he continues to behave like he did at his previous club. Well, I'm actually interested in Aston Villa right now, Unay Emery has brought in quite a lot of names. some of the names are Donyell Malen, Marcus Rasford and Marco Assensio. I believe if this coach has a plan for his squad, that's why he brought in and loaned some players. but that will actually provide competitive competition within Aston Villa, so the players will work hard to perform much better. by the way, this is just my assumption in the assessment made by Aston Villa.