As you alluded to yourself, that issue was arguably more down to how Tuchel set us up against the smaller sides. Lest we forget, this team were still the same team that were able to score goals and put away the smaller teams under Lampard. His downfall was obviously the tactical and defensive side of things, which Tuchel has helped fix/improve. So, Tuchel needs to find the balance on how he has us play against the bigger sides vs the smaller sides. Maybe use the back 4 more instead or use more attacking personnel in some positions. This pre-season and early parts of the season might also give Tuchel more time to work on our attacking plays, attacking patterns etc.
Are we really in a do-or-die situation if we don't get a striker this summer? I don't get this constant doom-and-gloom. I don't know if it's because people are used to us winning things every season in the past, used to having a team that's the finished article and hence don't have the patience but we should remember that this team are still relatively young mostly and have plenty of room for growth and improvement. There is still more to come from this current group of players. Yes, there are certain areas in the team that can be improved on but at the same, we are also not in a terrible situation like some have made it out to be if we don't sign this player or that player.
If we can't get Haaland or Lukaku or whoever, then maybe the next best solution is to find a midfielder who scores goals and creates chances. Because right now, our midfielders are averse to passing the ball forward and can only score if it's from the penalty spot. We used to have midfielders who can score goals from open play - Lampard, Ballack, Essien etc. Heck, even Fabregas used to do it here and there for us, even when we played the back 3 under Conte, to go along with his chance creation.