I frankly don't think the costumes change much less now than they ever have.
Many will disagree with me but...as for stormtroopers, I admit the endless variations have always kinda bothered me. I personally feel like stormtroopers as seen in ANH were originally conceived as elite universal soldiers, outfitted to be able to fight anywhere, even in the vacuum of space and ranked above standard Imperial soldiers. Sure there were accessories that could be added but the base armor remained generally the same. I always though the original idea was that standard stormtrooper armor was multipurpose, adaptable and capable of being suited for any situation.
Of course ESB comes along and they decide to introduce the so-called snowtroopers, cold weather stormtroopers. Suddenly we now have troops that seemingly have specialized armor for cold combat that fill a niche that apparently regular stormtroopers can't. Now we see that "regular" stormtrooper armor is limited in some regards and isn't so universal. However, in my own headcanon, I much prefer the notion that snowtroopers are not in fact a variant of rank and file stormtroopers but rather are Imperial Marines. For the purposes of the Hoth battle, their skirted helmets were accessorized with a heated mask and they wore winter boots for snow combat. The armor as we see it is otherwise just what they look like in any circumstance, not just cold combat. They are separate from the stormtrooper corp and thus wear totally different armor. I could buy that if it was canon...which it isn't. Then of course RoTJ introduces the scout trooper although I don't really know what they offer that a standard stormtrooper couldn't do, besides look cooler of course. Obviously their armor was heavily influence by real world motocross gear. In the real world, I'm sure the costumes were more comfortable for the actors to wear but I imagine stormtrooper armor wasn't meant to actually be awkward in canon.
Besides all the variations that got introduced in the EU, the PT comes along and especially in ROTS, we see endless variations and customization of all kinds of stormtroopers (I guess called clonetroopers so we wouldn't forget they were clones?). Even in the Disney era, we get shoretroopers (Huh? Stormtroopers dedicated to...erm...fighting on shores?) and so called swamptroopers, although I think they were actually just standard Imperial soldiers and not technically stormtroopers.
Regardless, over the years it seems like we've gotten more and more highly specialized, niche stormtroopers variants for every possible biome and circumstance. I'm sure they sell toys and it is fun to see new designs but in the back of my mind, I think it takes away from what stormtroopers were potentially meant to be back at their conception. Nothing I can prove of course.
Going on a tangent but in RoTJ to an extent, and especially in the Disney era, when stormtroopers started to be depicted being knocked unconscious by melee weapons and in some cases, armor actually being shattered(?!) by sticks, I could only shake my head. Apparently the armor literally is worthless. Disney has also seen fit to establish that apparently stormtroopers are known even in the GFFA for being bad shots (Obi-wan's comments be damned) just because our heroes had plot armor in the OT and it was something of a joke among SW fans. In the first season of The Mandalorian, Mayfeld mentions he was a sniper not a stormtrooper, as a commentary on his ability to shoot, and we actually see two scouts trying to shoot a target at near pointblank range and still missing, to comic effect. With the way they are depicted, especially now, I can't imagine why they were ever feared or effective.