1. Given that I play several jobs that have cast times and are often expected to stand in melee range to do them, absolutely. It's not difficult and to believe it is shows you never played a Caster. The job gauge meter is a walk in the park and you're acting like SAM is the only job with two meters and cast times as melee. RPR says hi, as does MNK and DRG with their far more unforgiving meters if you happen to get caught out. BTW, in most content, if a Caster gets slapped by a PBaoE they typically die, you don't unless it's Savage + content.
2. It absolutely is a weakness given MNK literally will lose uptime on certain mechanics, if you aren't using your ranged attack at all when you cant be in melee range, you're not playing your job optimally and think you have more to worry about than losing Kaiten.
3. DRG weaving issue always existed, the fact you don't think it did, that they literally could not double weave and were pigeonholed into single weave because of their animation locks shows you never played DRG at an optimized level and are probably not in a position to give feedback on that. You know how many DRGs felt a huge sense of relief that they could finally double weave properly? I'm going to wager probably not.
"Because of people that played the job"
On this we agree, if a job has a low floor and performs incredibly well even at that low floor, who is going to play it?
Everyone.
Taking away Kaiten didn't change SAM into a different playstyle, they haven't undergone some full rework like SMN and MNK or a mini rework like AST ..
They are the same job with the same kit
They took one button away and spread the potency across your kit. It never ever was a big brain job, it just created a lot of false superiority because of it being a top dps.
And you know what? It's perfectly fine for a job to be pick up and play, easy to learn
Ya'll just need to stop conning yourselves into thinking SAM was ever anything else.