I'm sensing some OE or faulty gear here if you're having to crank the input gains all the way up.
That may very well be, but it's that way for every channel, every mic, & every sound source (voice or instrument) so it's not isolated.
I never use the compressors, so I have no idea how well they function, and I don't insert anything because I don't want to lug outboard gear. If you turn the compressor knobs all the way down, they have no effect on the channel's output, so the channels are still usable.
Except that there's still no insert for those channels to use something better/different even if you wan t to.
Tonight, my acoustic trio played an outdoor gig using A Mackie ProFX16 with Beta 58s (instead of our usual Super 55s), and the input gains were set a little below noon. The channel faders were all set at about unity, as was the main fader. It was mondo loud - we were all going direct into my JBL PRX715 mains and PRX 612 monitors. When we left the stage, I replaced the Betas with SM58s for the next band, and didn't have to boost the gain at all.
That's what I'd expect. Doing radio mixes, there are no speakers involved - main outs go to a channel on a studio console. I have to rely on the board's meters for level & my own ears for distortion.
If I ever needed more auxes, I'd fire up my Presonus 16.4.2, but it's a lot of board for a trio (plus drummer). I'm happy with my Mackie boards and the pre's are OK, but they don't compare to the ones that were in my former Midas Venice 24, which I sold because it was just too big and heavy. I sure loved that board, though.