> - They are loud
That really depends. This one seems pretty quiet: https://youtu.be/rGM8Y6yal-8?t=337, but buckling spring keyboards are obnoxiously loud (IIRC from my childhood).
> - The keys are massive and ugly
That's only true if your preference is for laptop-style keyboards.
> - Massive travel time (So slow to type on)
IIRC, one of the main benefits of mechanical key-switches is that you don't have to bottom them out to activate them. On my keyboard, there's at least 50% more travel after the switch is activated, and the travel-to-activation doesn't seem massively different than a laptop keyboard.
Also, non-mechanical desktop-style keyboards require the most travel time of anything.
> Sure they are a bit more customizable, but is that really worth all the drawbacks? Especially the worse typing, which is the main point of a keyboard.
Honestly, I think one of the better arguments for mechanical keyboards is that most non-mechanical keyboards were designed with cost reduction as the top priority (or in the case of Apple, thinness for its own sake). I guess if you're used to that, it's fine, but gunning for cheap usually leads to quality compromises in other areas.
The most annoying things regarding mechanical keyboards is that the culture around them has weird obsessions (like stripping things down to the fewest possible keys and using stylish custom keycaps). For instance, when I was searching for a quiet keyboard video, I found this one (https://youtu.be/O3-9ttpaU0E?t=57), where they guy misses the point and thinks the cool thing about Symbolics keyboards was the keycap style, when it's really the seven modifier keys.