MNK is only hard to master now if you've never played it before and you're not used to it.
Which it was before too if we're talking about people who seem to have boosted and then jumped into it and been all like '' ermaghurd I can't member which side 2 hit on and I haev to looky at mi buff and debuff tooltips wats dat? ''.
What exactly about MNK is difficult to master now?
I'd say that the previous burst window was more difficult same with SAM now you can't even drift anymore there's no more real decision making to be made that actually had a real impact on your damage.
On MNK and SAM in SHB you had to actually have a deeper knowledge of the Jobs and make decision that would decide whether you'd hit the burst window properly or not and there was more adaptation that needed to be made that added extra skill ceiling to the Job.
I love new BLM but new BLM also got significantly more tools to cast while moving and avoid overcapping Xeno + double Sharpcasts and way longer Thundercloud procs.
It absolutely became easier to play, a lot easier.
Dropping your Eno timer doesn't screw you as much either.
The changes to these Jobs have been made to make them less difficult and less skillful to play it's just objectively true.
Maybe the reason why you thought that they felt clunky was because you didn't play them properly.