At this point will FFXIV collapse if all mods and third party tools disappear?

Mods are what keep this game alive after the initial msq nonsense, and whatever raid(s) they add. Hundreds of hairstyles, glamours, and QOL changes that make CBU3 look like amateurs in comparison.

I even saw a mod that fixes the washed out dye colors on some glamours. If I'm going to dye something pure black, it better be black; not washed out grey.

Even with the 2 dye channel "feature" that took them 10 years to implement, you're still going to deal with a stupid dye system that decides randomly whether something's going to dye as it should or washed out.

Put a modder in a FF dev position and watch what happen's to the beloved quality.