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.
I don't really hate anything in the DAWs I use, which includes Ableton Live. The only niggle I have with that is that the controllers in the racks don't always reflect the changes accurately.
I didn't like Logic when I used it a few times years ago (it just seemed limited to being OKish for recording, and everything else was irritating to me), and I hated Pro Tools for its linear, restrictive workflow. I liked Cubase, but didn't bother to buy it, as I ended up with Ableton Live.
However, you seem to not want any of the mainstream choices anyway. Have a look at Renoise and Mixbus. Both are cheap (under $100).
Harrison Mixbus is basically Ardour, but a bit more polished, with much better EQ, support, and mixing capabilities. It's basically a Pro-Tools like layout and workflow, but it has its uses (and it has a subtle in-built tape/analog emulation, so a lot of people feel it sounds better overall).
Renoiseis just something else altogether. I love it, and I would rather work with it than any other DAW, just because it's fun and encourages creativity. (I use Ableton because I needed it professionally, and it ended up being easier for me to stick to one DAW). The tracker workflow of Renoise isn't for everyone, but I found it quick to create with, and focused more on listening to what you're making than looking at waveforms of it. There was nothing at all that I hated about any of it.
I've also used Bitwig and liked it. It's a different workflow again, but is pretty similar to Ableton Live in a lot of way (session/arrangement views, a sort of modular design). It's improved recently, but I haven't used the new (3.0) version; basically it looks more modular now, and the sampler is supposed to be a lot better.
I felt Renoise was just more fun and better designed overall, but I like weird and experimental things, and I like software that knows its limitations and isn't embarrassed by them.
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