The Mug change, predictably, feels like garbage.

[butchersblock]

And yet if you look at opinions about Ninja the common one I found on Reddit and few other places was once again too much work required for too little of gains. Also I probably have to learn how to use data better because... I don't think 6.0 Ninja was that meta in Asphodelos considering in submitted data the Ninja usage was between 10 - 20% depending on a boss.

You're cherrypicking here. Ninja is nowhere near as complicated as some people on the forums would have you believe, take that from a Ninja player. It's been extremely meta since Shadowbringers, and was only weak at Endwalker launch, which was quickly fixed in 6.05 and 6.08.