about the practice mode: it does some things really well but it also lacks absolutely basic stuff, like showing move properties and frame data in the move list. if you want to find a certain stituational move, you gotta execute the whole 100+ move list every single time on hit AND block just to access the move data; and lets not even start about finding optimal combos by yourself. complexity itself is usually no issue for me - i did learn VF5 to a degree. but tekken - i dunno, i have a gut feeling that even the core community wont be as happy with it in the long run, opposite to the initial hype.
It goes back to Tekken being a legacy game and different idea about new players comming in now. There is no way a new player is gonna go throu even half of the moves of one character, it doesn't even make sense, since nobody is using even 1/5th of it anyway.
The idea for new players is to watch their own replays, where they can see all the frame data live all the moves being used with game giving them tips which should they duck, which should they punish, how should they punish it. You can pause, play, try anything at any point in the match. It's trully amazing. It's way more efficent way to learn than go throu lets say list of 20 moves in MK and see frames on it and... good luck.
As for optimal combos it's a mixed bag, the game gives you basic and decent ones but it doesn't show you everything for every scenario(walls etc..) and that's fine. Learning optimal combos is the last thing a new player needs to learn. By the time a new player learns everything important he won't have troubles with optimal combos.
I really think Tekken 8 practice mode is amazing, the best in any FG till date by a long shot. That being said obviously not everybody gonna like the game, nothing new here, some people didn't like Tekken before and still don't. Nothing wrong with that but there is no denying the fact that Tekken 8 is a complete package, a good game/product.