^This. I'll say it plainly:
it won't improve fitness, and if Pilates is the extent of your resistance training I honestly wouldn't even bother.
It is simply a tool to increase your protein macros. If it's a weight gainer, it'll also increase your calories and carbs as well. It is no different than adding a can or so of tuna, or an extra piece of chicken.
Truly, the only benefit of proton supps is that it's often much easier (and sometimes more convenient) to drink something than it is to eat something.
Protons won't turn you into Captain Marvel, help you run longer, etc. An increase in overall dietary protein could improve body composition, but that's debatable and somewhat moot.
If you're not actively trying to build muscle,
why would you want more protein? If you can't answer the underlined you definitely don't need it.