I'd like to turn my 500,000 poly model into low poly to make it game usuable. However I cannot bake due to reasons. How can I do this without losing noticable detail and destroying the uv map
$\begingroup$
$\endgroup$
If baking is of the table because of the 'reasons' you've mentioned, there is simply no way to reduce the poly-count AND retain all the relevant detail. Less information to store and process means... well, less information.