I understand a professional not wanting to learn a new UI for something as complex as graphics editing, but if you are admittedly mostly using it to resize images, I can't imagine why any other tool, including the infamous Gimp, would be so hard to "learn"?

I think I was overstating the extent to which I only use it for resizing photos.

Why not use Preview? For most things, like resizing and cropping, and rotating, it just works

It doesn't do compression or format conversions.

It does do some format conversion and have some support for compression settings (if I understand you correctly). Under the File -> Export menu you can choose between some formats [0] and when applicable choose compression level, e.g for JPEG.

[0]: On my machine: HEIC, JPEG, JPEG-2000, OpenEXR, PDF, PNG, TIFF