I never understood why it's seen as some insane disrespect to take a guy off 30 minutes in. Ten Hag can always just say it was tactical and he was the one who got it wrong, since it was clear by about the 15th or 20th minute that we weren't able to progress the ball into the Newcastle half, and Antony is better at that. Or bring Amrabat on, move Bruno out right and say you were wrong about not needing another midfielder. Hell, he could even have taken off Martial and thrown Rashford up front, or brought on Varane, Reguilon or Lindelof and gone 3 at the back.
There's been this weird stigma to getting hauled off after 30 minutes instead of 60, but it makes no real sense and I can't imagine it'll still be a thing in 20 years.
Sometimes coaches get it wrong, or a guy is struggling. You can throw the guy back out there next game. Instead, we constantly see teams clearly on the road to losing waiting until it's too late to make a sub. We couldn't handle Newcastle's pressure with Rashford sulking on the right, and waited until we were losing 1-0 to make a change instead of doing it at 0-0.
I think the way to fix it might be to allow a player subbed off to come back on. Still counts as a sub. Rashford comes off and maybe he comes back on with 20 minutes left for Garnacho and a point to prove.