This is just wrong. At the start of last season Rose was trying out a lot of different things, but using a midfield diamond was perhaps his most common setup. Going down 0-1 after 50 minutes against Bayern is anything but spectacular failure (we're talking about a team which kept trashing opponents even in the CL), he then tweaked his formation, by bringing on an attacker, actually showing that he can adapt. But doing so by staying true to his principles and not "a complete change of how a team usually plays" as you put it.
You mention Klopp: he used a 433 in 35/38 games last season, the most visible adjustment to opposition is probably what midfield trio he picks. You mention Guardiola, when does he ever "completely change" how his team approaches a game? I think the most common criticism of him is that he actually does the opposite.
Solskjaer sometimes changes formation, but when does he just pick an entirely different tactical approach? Like how often do you get the impression that he tells the team that he wants to play an aggressive pressing game or positional football? So for a couple of games he used a 4312 instead of 4231 against top teams - the overall approach was still the same. Passive, hope for a counter. If that constitutes a plan B, or subbing on a defender/attacker based on the game state, then were not talking about having a plan B, were talking about having a plan F, G or H, because that happens several times a game.
One of the very few coaches who actually comes close to what you say is Nagelsmann:
And he's quite special because of it.