It's just that Tuchel has problems with his goalkeeper. In fact, Sven Ulreich cannot be relied on, especially in big events like the Champions League, we can refer to Bayern versus United. Sven Ulreich, really played far below the standards of a quality goalkeeper. If Neue never recovers from his injury, in the winter transfer window Tuchel will inevitably have to look for a goalkeeper he can rely on.
I agree with your opinion on the goalkeeper problem. It is a visible issue for Bayern Munich now. Maybe they don't have a big problem about that in the Bundesliga for now. But the Champions League will be much more different. We have seen this from their first group match already as you know.
They conceded 3 goals from Manchester United. They must be grateful for their scoring performance that they still managed to win. But this problem can cost them the Champions League after getting past the group stage. They might have serious issues against a title contender for example.
I think they should give some chance to the new guy Daniel Peretz sometime. Who knows maybe he would perform better than Ulreich.
Bayern Munich was never a team with bad financial power and they could easily hire another goalkeeper in the summer with the money they can spend for it but currently, the only hope they can have is just their old and experienced goalkeeper Neuer. Neuer is getting recovered and I think he is going to play for his team soon but I don't think if we can expect to see a good performance from Neuer when he returns.