Endgame raiding is heavily based around tightly aligning team cooldowns in large burst phases every 2 minutes. SAM's natural rotation doesn't align cleanly with this, and there are two ways to deal with it- using hagakure to throw away part of your rotation so everything fits, or slightly changing your rotation every time, not only for more damage, but also more flexibility with mistakes or downtime where you can't hit the boss.
A key part of that is using meikyou shisui to accelerate parts of your rotation, and entering burst with full sen/stickers but with a partially finished combo, and using that after midare+gaeshi to get a sticker for higanbana instead of using meikyou. Essentially, it lets you easily move your rotation up to 6 GCDs ahead or 2 GCDs back, and you can do so closer to burst. Since you need gaeshi to be the 2nd GCD in your burst, the change complicates the timing for accelerating things, and makes the latter impossible as meikyou overwrites your combo. You have to fall back on using "standard" hagakure looping, and that requires planning 8-10 GCDs ahead and makes it harder to adjust midare timing to take advantage of how it has double the range of regular attacks.
Without this flexibility, there's a very clear prescribed rotation and you just have to not screw up. IMO that's horrendously boring and more often than not just feels bad. At the risk of being melodramatic, imagine playing pvp where there's no value in pressing the advantage, and no back and forth where losing the opening engagement means that you can at best squeeze out a draw unless the other team throws the game. It's just a lot less fun.
To make things worse, the only other job that has this level of depth and freedom is BLM, and it looks like they're also getting their flexibility taken away. For a lot of people nonstandard BLM was the pinnacle of EW job design so these changes feel incredibly tone deaf given that they contradict the dev's stated goals of listening to the playerbase and addressing pain points.
Ngl, none of this is particularly surprising given what happened to kaiten, but if annotated powerpoints saved character creation then I might as well format this feedback seriously.