Problem:
how to exclude specific taxonomy term from search result

Solution:
If you do not added category search filter, you will just require to add the taxonomy filter and select the option "NOT one of the following" and select the category you want to exclude from search.

You can find the proposed solution in this case with the following reply:
https://toolset.com/forums/topic/custom-search-filter-only-certain-product-categories/#post-1770021

Relevant Documentation:
=> https://toolset.com/documentation/user-guides/views/filtering-views-by-taxonomy/