How to clean up CSS/templates by parsing a website?

Question

css

There is a large website with 280 layouts and 50,000 pages.
In these 280 layouts, there are 3,000 type constructs class="* * *",
800 out of 3,000 classes are unique.
There is a general site style and unique template styles for 150-250kb, weighing 1,500 selectors.
What I want is to build a page / style tree (style map), remove unused styles,
unify the practice of using selectors. The most obvious thing is to redo everything, but I would like to
hear some other practices in such cases, from my own or someone else's experience.
I need your ideas, tools and practices (glasses and clothes)!

Answer 1

For a style map, it would be very clear to rewrite styles in LESS, and then unused ones will be clearly visible