I‘m not too disappointed that we didn‘t bring anybody in. I suspect that we have enough work trying to drill the basics of the intended system into the already available players. I don‘t think we have the time to try to add new players to the mix.
Regarding the public opinion it‘s a no-win situation for Rangnick anyway. We‘ve been doing things for the sake of doing things for years now, and I can‘t see any big improvements. If he fails to reach the CL spots, everybody will claim it‘s because he didn‘t buy player x in January. If he bought somebody, it‘d just increase the pressure without guarantees.
For me personally, I‘m happy because we‘ll either be able to see a noticeable change in performance or we won‘t. And we‘ll know that it‘s his failure if it doesn‘t work out. He won‘t have signed a new player (maybe like Bruno) who carries the team into peak form and rides a wave of momentum, creating the impression of real progress, but without having made any systemic changes. He will have nothing to hide behind.