As for Amorim, he may take years to achieve what Ole and Ten Hag did. He has to deal with the financial struggle faced by Manchester United at this moment. He clearler confirmed he won't able sign a new player without selling a player. 1:1 rule is applied.
About Antony, his price is not worthy with what he given to the club. He's one of wasteful transfer iniated by Manchester United. However, Casemiro's transfer is also as bad as Antony's transfer.
So when it comes to spending money on players, of course Glazers still have the last confirmation, but they are not making the decisions on who to sell and who to buy, or for how much, they are just given that by INEOS and they have the last say of confirming what INEOS does, or they could veto it if they want to, but I have never heard of them veto anything so far. With Antony and Casemiro type of transfers, if Amorim does better, then even with 1to1 ratio situation, he could do fine, all he has to do is just not get that type of bad transfers, if he could get decent players then the team could recover and do a lot better.