Rather than saying what's frustrating about a compact, I'd rather set out what I want from a system. If the compact - or whatever - meets the requirement then I could be happy - but, hey, remember what I wrote about being happy.... and not hankering.
- Good battery life. I want a camera to be good for 3-4 dives in a day without changing the battery. Figure, say, 1000 images.
- No write delay on the cache/memory card.
- Effectively no shutter lag. Not a hint of lag. None.
- Precise, instantaneous framing in a bright, clear, big viewfinder - preferably one that can be fitted with a 45-degree magnifier.
- Precise and rapid framing by the zoom (if I'm using a zoom)
- Fast, reliable AF with manual override for macro
- Ability to stop lens down sufficiently to achieve black backgrounds
- A good range of optics: at minimum: FE, 16-35 (for big fish), 60 and 105 macros - or equivalents
- Camera reliability and good servicing.
- Suitable and well-designed housing that will allow all controls to operate and cater to TTL and vacuum valve.
Those would be for starters.
As Chris says, if a system covers all the bases for you, go for it. But, again, don't then hanker, wish, sigh......