hmmm... which interface do you use?
blockchain is the same, but interfaces and thus -> servers, are not. the most wide-spread are: peakd.com, and ecency.com (after the hive.blog itself ofc). as I dont use hive.blog at all I cant tell does it spoils photos a bit or not.. back in the day I witnessed that ecency does a better job to the photos...
by the way! peakd makes it possible to have images clickable for high-res automatically. otherwise you can only get it manually (editing the actual post's code, which is... mehhh....)

Even uploading high quality photos (which took a lot of time) did not solve my problem.

Personally, I dont have this problem. I guess that you are getting what you uploading. hmmm.

Below is a test upload (made via ecency)