We need new fullbacks, two new central midfielders, a replacement for Eriksen, a replacement for Toby, probably another attacking player who provides better depth than Lamela .. a backup striker would be nice but Son is an able deputy.
We're obviously not going to sign like 6-7 players though (and shouldn't do, that rarely works) and that's why ignoring last summer/january was such a silly mistake, because next summer now we're going to need to be incredibly busy in the market due to replacing players who already left, injured players, and ones who are leaving .. all in one swoop. I imagine we'll continue to ignore the fullback situation, bring in a young player to replace Toby, probably someone like Maddison for Eriksen and maybe Grealish.
It's also all going to be twice as difficult if we do miss out on CL this season, can't be stressed enough how important that is to us.