B4 is a meme machine that is it. Be honest with yourself and notice no competitive player or team uses this commander seriously. How about you try to use it yourself and see how difficult it is to play?
It's not my fault if high competitive players would rather play the same meta over and over again trying to reach a rank that really doesn't matter and don't want to experiment. I play with a partner and we've reached top 30 in team-of-twos because meta players have a hard time countering meme strats and unconventional strategies... one of which is very aggressive play with the B4. I've stopped plenty of axis advances because my B4s would devastate their forces before they could properly push, and have for-mother-russia pinch them after they had to retreat.
I've also had plenty of times where my B4s would be shelled by LEFHs from across the map (by counter-battery) or wasted 90 munitions because the B4 shell flew right by a tank that was barely moving, or hit a twig and exploded before it reached its destination. I've also been properly countered plenty of times by stuka dive bombs and shrek flanks.
So yeah, I've played with it plenty of times, and it isn't necessarily difficult. I wish I could replace all the ML-20s with B4s because in my opinion it's a million times more useful than a shittier LEFH with no vetted abilities to use for some stupid reason.