I have about 15 resource packs all separated doing little different things (one that just changes my elytra texture, one that makes ancient debris lime green, etc.) so I can choose exactly what combination I want in which version of minecraft (and also share specific parts with friends).

1.18 and before was fine with this. 1.19 takes about 4 minutes to load them (during startup or changing in the resource pack menu). I manually combined all of my textures into a single pack and it took the expected 5-10 seconds.