Premiere and all the other major editing programs don’t do a great job with H264 and H265. They are not designed to. Premiere can export to Cineform (in a MOV container). While this will be a large file size (over 100 GB for 2hr movie) it will be smaller than a comparable Prores codec and look better than Prores. And it will be a perfect master of your project. Then you can re-encode it to H264 or H265.
EDIT: Also some films have so much grain, especially older ones, in order to maintain the clarity of the grain you might end up with an H264 or H265 file larger than 10 or 20 GB. An option might be to do some DNR if a smaller final file size is important.