We 100% would have drawn or lost a few matches more without Antony. The same argument can be made for every player bought last summer. Top 4 was clinched with 1 match to spare and Pool were playing for nothing the last week, so the margin is smaller than it looks. Don't give me any nonsense about better alternatives being available, the decision makers above and around Ten Hag are incapable of finding/buying them anyways. You can make the argument that Elanga/Pellistri at RW would have yielded the same result but I doubt many will agree.
As to the bolded part: if you want managers to care about signings for the long term at reasonable prices, everyone will need to stop blaming them for literally everything that goes wrong at the club. This is also why we get bent over for everyone we're in for, because the managers will get sacked for 3 months of bad results no matter the circumstances and they join the club with a pitiful squad to begin with, so every transfer is life and death. Even considering this 3 of the 5 signings signed off by ETH last summer were 24 or younger and the age profile of the targets this summer seems to skew younger as well. Players aged 29+ are generally cheaper and and more likely to make an immediate impact, but you have to replace them in 2 seasons, but most United managers don't care because nobody makes it past 3 years here anyways.