Yeah, the advantage of limiting colours and sizes to preset multiples made life a lot nicer for a while. Very easy to keep things looking consistent without needing to re-reference specific values. But they keep making it more and more easy to do things like p-[7px] which rather defeats the point and there seems to be talk about changing the scales to just using px/rem numbers which feels like a complete abandonment of the idea.

Customise the tailwind config for your design system, add additional CSS in a css file for specific needs. Generating arbitrary values on the fly just muddies the system back up again.