If you are down 1-0 late in the game and you aren’t creating enough threat, like for like often isn’t enough, why not go for it. Martinelli already drops back to cover on defense and from what we saw in the United game Trossard does too, you get a better offensive player with Trossard or Smith-Rowe, players that can actually create space for themselves in the box, and don’t lose a lot defensively
The problem tactically is EVERYTIME we went wide to Saka or Martinelli it was a 2v1 at minimum, sometimes a 3v1. I was hoping we would bring on Tomi for White, who was having an absolute stinker (move was made but far too late), and Tierney on for Partey and move Zinchenko into midfield. And tell Tomi and Tierney to bomb forward at every chance to make space. Instead we didn't see any of it, and we predictably became "keep going to Saka or Martinelli and hope for some magic". ESR was injured but Trossard for Xhaka would have been fun to watch. Or we should have gone a tactical change when Partey came off, ran with a 4-4-2 basically with Martinelli and Nketiah up top, Trossard and Saka on the wings, and then Xhaka and Jorginho in the middle with the same back 4. Instead we did nothing to change the game state and let Everton dictate everything from about the 20 minute mark of the match.
With regard to Partey, the problem was that we took him off before we went down a goal---probably because he still wasn't completely healthy from the rib injury. But once he went off, it was very unlikely (right or wrongly) that Arteta was going to take off the other (and that point only) adult on the pitch in Xhaka. I agree that I think he should've, but he just values his presence in the side a lot.