At least that makes sense -- rebels using imagery and symbols similar to Old Republic symbols makes sense since they're the Alliance to Restore the Republic. Prior to the Clone Wars, the Republic using the designs of some of their greatest enemies in a widespread capacity is weird and doesn't really make sense imo. Mandalorians and Republic had a negative relationship for almost their entire existences -- even by the Clone Wars, the pacifist Mandos had no interest in joining the Republic. It's like if the Allied forces, NATO, US, etc. militaries started wearing long black coats with red armbands.

I prefer the clones being unique and a telling design choice: the armor of some of the greatest enemies the Republic & Jedi have ever faced is now worn by the soldiers of the Republic who are essentially Mandalorians themselves, ultimately usher in the collapse of said Republic and finally, in a way, defeat their greatest nemesis via the Purge.

They definitely look cooler but imo, they should have really differentiated the Republic soldiers from TCW. KOTOR already had the 'issue' of looking a bit too much like the films desoite being thousands of years prior but at least they used different coloring, different designs, etc. Repuvlic troopers just look like 212th clone commandos at a glance compared to say, KOTOR's Sith troopers which obviously emulate stormtroopers without really looking too similar.