Basically,
Pay to win the higher you go.
Little to no historical accuracy/hard evidence of most new vehicles that are prototypes and/or blueprint drawings.
There is always a new tier 8 premium that breaks the game.
Repetitive gameplay. Different game modes do not last long.
Matchmaking is based on vehicle class, not player skill.
No effort in presenting a new tank (one of the recent premium tanks was just a regular model in-game with a bulldozer blade. You need to pay for a non-premium tank model with a bulldozer blade!)
The damage model (or whatever its called) for each tank is not consistent with the actual model (the Chrysler K tank, for example, has two machine guns on the front, but the damage model does not recognize them as weakspots.) This goes for some to most of the tanks here.
WW2-built tanks and Cold War-built tanks overlap, causing unusual and sometimes unfair battles.
Excessive use of premium shells.
Artillery in general.
I've played this game since 2013, and I'm disappointed in what it became, and how it got there.