I think the issue is every game is breakable if the playerbase put enough time in to breaking it, you only have to watch speed runners of anything. The issue for FM is breaking the game was something players did just by seeking the best tactics, as a programmer myself I kind feel like balancing FM is a next to impossible task given all the permutations and possible set ups. There's no game that's ever gonna be balanced to the level FM needs to be.
I do think they made a mistake swapping the stuff they did for roles but it kinda makes sense along with letting them cover some flaws.
No one sets up a defensive by saying to their players, we gonna stand at exactly 17 outta 20 etc.. so I can understand the realism reason for why they removed them too. A manager is more likely to tell a winger stay on the touchline, stay wide etc.. as opposed to setting his width to x out of 20.
The issue for me is in patching those huge exploits and changing to roles, they removed a lot of the fun.