I think this is a fair reflection. There are some tactical tweaks that do next to nowt, some that do what you expect and then ones that you think might be logical but then actually break your entire tactic down. I think the reason for this is that it's not (usually) just the tactic that you have to think about but the players you're inputting into it and the behaviours they demonstrate. As such you could make what seems like a logical change but due to the player's mentals or physicals suddenly they're struggling. An example I'll give is of my 4-2-3-1 dm tactic which presses high but when teams come at me they get in behind. Now, I have a higher D line and drop off more already tagged and I don't particularly want to change mentality from Positive because I've found that makes us sterile and invites more pressure that way, so early on my next logical step was to lower the D line when this happened to standard. Now, in an early save this seemed to work but when I played with a lower league team suddenly my defenders who played well enough in the Higher D line were suddenly all over the shop and the goals I conceded were stupid. It took a couple of games to realise this was now a suicidal thing for me to do so instead I knock both the CBs to cover and keep the D line and we defend better when a team tries to get in behind. Different tweaks and different results and it all depends on the intersection of your players in the tactic.
This is why, I am assuming, so many people get so annoyed with the game sometimes because you think you are doing something logical and then you absolutely fall apart. Add to this the impact of morale and momentum in the ME which I think also has a real visible impact and sometimes it can look like you are defying logic and do you know what? I'm gonna say kudos to SI for that because a lot of football defies logic.