I agree with you 100%. Playing full manual against CPU above professional makes the game go totally wrong. And the stats-boosting (that is in fact a cheat even if some people don't like the word) is lame. That's why sliders are blatantly needed to customize the game to your liking.
There's another bltant cheat that cpu does, and it's related to dribbling and general movement.
CPU ALWAYS knows were are you going next. You can dribble because your player is faster or because sometimes (and only sometimes) they react later to the direction change. But YOU NEVER fool them. It's impossible.
In the same way, when they have the ball and you approach to them, they instantly know and turn just the other way.
These things (reading the user input and reacting perfectly to it everytime, just as in sliding tackles perfectly avoided the same frame you began the sliding animation) should be toned down.
You should be able to fool the cpu the same way they fool you.
And by the way, CPU players in World Class or Legendary have less inertia than yours. You can count the frames in the turns they make, they are a lot faster (not measured, it's the feeling I and the majority of people have about it) than your players doing sudden turns.
If only there was an effort to put ERRORS in the CPU behaviour, the game would be even better, and it's not that difficult to introduce this things in AI, really. We're not talking about smart AI, just that depending on player STATS, a cpu player can be fooled and don't follow your exact trajectory 95% of the time.
As a last comment, something that seems absurd is that all this is aplicable in deffense and midfield, while in the final third things get a little softer and sometimes you can do things inside the area you wouldn't dream to do in midfield. And to me, that feels just the opposite to how it should be!