The most annoying part about being a football fan is having to listen to other football fans constantly blame managers for their tactics. It doesn't matter which team you support. It happens with every team, on every professional level. Am I really gonna listen to Armchair Bob, fueled by Stella and the power of hindsight, and value his opinion over a professional manager with years of experience, hours of research delivered to him/her by professionals before each game and exclusive "behind the scenes" knowledge?
The Dunning-Kruger effect is evident. You might protest and claim that you have watched football all your life and therefore don't fall into the "no experience" category, but you're wrong. You haven't managed a professional football team and you never will.
The worst culprit is the power of hindsight. Unless the team you support dominated the game by every reasonable metric, you can quite literally blame any loss or draw on poor tactics. You disagree with the selection of a player? Well, the player that wasn't selected would have made all the difference! You disagree with the formation? Ditto. Individual errors cost you the game? Well, the coach should have spent more time on X, Y and Z in practice! A more attacking setup than usual? Naivety! More defensive setup? Cowardice! The usual setup? Lack of creativity!
Ultimately it all falls back on one thing: the result. If the manager wins, then he/she got it right. In some cases people will claim that the win was lucky, though. It largely depends on the popularity of the manager and past results(I'm beginning to see a pattern).
The elephant in the room remains the same: you don't know shit. You don't know what the research behind the scenes have picked up. You don't know the thought processes and how the managers try to predict and counter each other. You don't know what is according to the plan or not. You don't know which players have performed in training or look especially motivated. You don't know which players are most suited to deal with the manager's tactics for a particular game. The only thing you do know is the end result. But you don't know
how much of the loss/draw came down to failure in tactics or in-game adjustments. If tactics and in-game adjustments are responsible for 20% of the outcome(which I think is a very generous number), then the majority of losses and draws aren't primarily gonna be because of this. And it's not like tactics are binary either. There are many grey areas and you can get some things wrong and some things right.
"So we can't discuss tactics and in-game adjustments then?". Of course you can! This is a forum after all. But have at least an ounce of humility and don't talk as if you definitely have the answers, because you don't.