People just say things. Graphics takes are particularly bad... Here's a modern hot take I just find ridiculous https://news.ycombinator.com/item?id=31385749

I don't know if I'd agree with you about most of the complexity, a lot of it seems nicely modularized off and handled outside the OS kernel proper or by hardware itself. I strongly disagree about Linux being 15-20 years behind though, but only because I don't think progress is so linear. X is old, yes, and missing some things, but it still works fine, and experiences are often no worse than Mac/Windows XP/7/8/10 and frequently better, depending on your needs. Apple in particular has always had bad experiences the moment you step off the reservation, and even sometimes on it (but Apple enthusiasts can make more complaints than me). Audio has been a mess, sure, though there have been periods of stability with Alsa and (though it took them long enough) PulseAudio. (I share your skepticism of the new hotness fixing things, back when it was Pulse and even the upcoming PipeWire. I've always been skeptical of Wayland long term.) For graphics, you can still play your 3D games at 4k@60hz, you can still hook up external monitors (and for years that has had a much better "just works" experience than it once did such that most people no longer need to touch the Xorg.conf file), for weird niches that still complicate the architecture Linux allows you to hook up more GPUs (I think Win10 has almost caught up though recently by allowing up to 12). IME works just fine if you need to type Japanese. You can still remote desktop -- even in the archaic days with X forwarding, but you also had VNC and these days NoMachine is probably the best. None quite as good as RDP, maybe, and that may be a limit of the architecture, but it's not like there's much complete absence of capability that could be used to justify that time gap as a measure of progress or an indication of how much catch-up needs to be done.

Meanwhile there are absences or near-absences when it comes to other things Linux has long had and as far as I can tell aren't really things in Windows or Mac for the most part. Having a window "Always on top" is available as a Windows extension if you know where to find it, but is not out of the box. Workspaces are another thing, very useful if you're on a constrained screen like a laptop, though I think if you know where to find those there's also some equivalent for other OSes. I'm more doubtful if there's an equivalent to anything like Beryl in 2006 (now Compiz Reloaded, sadly on life support for years, but I still use it) for eye candy or other nice window management shortcuts (grid layout hooks without having to use a tiling window manager, jumping windows between monitors or over workspaces, dimming non-focused windows, arbitrary magnification and easy zoom-to-fit-screen hooks, I could go on).

I will grant that HDR support on Linux is missing entirely (I was recently reminded of this when I almost upgraded to a new HDR monitor). Supposedly annoyances can happen when mixing monitors of different pixel densities. But overall, the thrust of my comment is again just that I think it's hard to lay out a flat line of progress where you can clearly say Linux is 15-20 years behind.