@bluespeckHi BlueSpeck,
Many thanks for that feedback ...
Glad to see you are a Mac user

I've been using Photoshop since the early 90s, not long after Adobe first acquired the license from the Knoll brothers.
I persisted with CS6 for years after Adobe converted its products to an annual license, and finally had to convert to an annual license after MacOS stopped supporting 32-bit apps. Adobe's crippling annual fee started hurting - at the end of 1 year, I refused to pay again, and looked for an alternative.
I downloaded a trial of Affinity Photo - it was so good, I bought the software the same day - for 1/10 the Photoshop annual fee - now I own it forever.
Making the switch was very clean - a bit like buying a new car - its feels different, but driving is the same.
Affinity is almost a direct replacement for PS - but includes astronomy stacking and AP-specific macros all in one package. It's fantastic, and well worth the switch. The cash I've saved from not buying annual PS licenses paid for my new telescope !
Like you, I wish there was a single app that would let me catalog all my media, including FITs.
Graphic Converter is great for browsing images, and for converting FITs to other formats, but isn't really designed for cataloguing.
NeoFinder is the best overall - it creates catalogs from many media formats, including FITs.
I recommend installing the QuickFITs plugin - it lets you browse FITs files in the Finder - and also displays basic metadata - very handy !