Outdated military doctrine, low numbers, being a resource hog, as well as it being a one man turret and usually no radio made it not great. But it had decent cannons (for the time), and stupid good armor (for the time). Its a mixed bag. WoT definitely does it dirty (especially because it won’t let you use both cannons), Warthunder does a much better job representing it. The Char B1 ter was and upgrade of the B1 bis but it never saw combat (they were getting evacuated to the UK but the ship they were on sunk off the coast of France).

Edit: Overall a good tank for the time, but would have become very outdated very quickly if it continued service later into the war. There’s a lot of reasons why the Germans didn’t really use them in combat when they captured them