I've been using Ardour since 2002. It's certainly grown a lot since then, but has its issues, especially in the UI department. Your comparison to GIMP is a pretty fair one.
There's a good (and cheap!) way around this, though, and that's Harrison Mixbus. It's based on Ardour, but adds a very nice GUI based on Harrison's consoles as well as some of the best compression and tape saturation effects I've used. There are quite a few how-to videos on their website.
The best part is that often - like right now - they run a special where it's only $19 - it's usually $89.
A bit late, but what the heck.
Harrison Mixbus is based on Ardour and is easier to use, but slightly less powerful.Given your needs and you liking Ableton, an interesting one might be Bitwig.
A bit late, sorry.
Reaper is good and cheap, but definitely not the cheapest among the good ones. :-)
Here's another good one: Harrison Mixbus. Based on Ardour which is even cheaper, more powerful but not as immediate.
This might be a bit radical, but your question reminded me of this video showing the use of a (good) SSL Channel Strip plugin on each channel to not only to establish some “analog warmth”, but also to provide a standardized set of channel strip functionality across all tracks:
The video shows a Waves plugin, but I’m keen on Brainworx SSL console plugins.
The general point is to apply an “analog” feel to tracks that were recorded digitally.
There is also Harrison Mixbus, a DAW that is designed to simulate analog Harrison consoles. I like the sound and intent a lot. The UI takes a bit of time to get used to. To me it seems a bit “retro”. You might want to check it out:
https://harrisonconsoles.com/site/mixbus.html
There is also Waves CLA Mixhub that attempts a similar kind of thing:
https://www.waves.com/plugins/cla-mixhub
There are some caveats to that one, though, because it’s sort of it’s own mixing system overlaid in a DAW. Check out reviews before committing to that one. The sound is great, though, as is the sound of various other Waves CLA plugins, all modeled on analog gear and workflows.
i was doing radio production (now old geezer)
win7 ruined my workflow so i jumped to exclusively Linux when XP ended
but i have a lot more analog gear and hardware than software
(old-school is cross-platform, zero latency, no drivers!)
you must have invested a lot of hours to learn and configure all 3 of those major packages
a lot of it is transferable, but there are some bits of 'windows logic' totally divergent to Linux that can block progress - just getting JACK to start up can be a real pain for some.
I agree open-source packages are not good enough for professional use.
if i had a paying gig and needed a professional tool, i would buy Harrison Mixbus most audio professionals would know how good their products are
but as i am happily retired will probably be using the open-source equivalent DAW (Ardour)
I don't expect Linux GUIs to ever be all fancy shiny and skeuomorphic to suit some peoples sensibilities
the eye candy doesn't make the final mix any better,
but IMO a good minimal Linux audio path (ALSA and maybe JACK, but not pulseaudio) is what makes it worth my time and effort