I think there's a few aspects to this whole subject.

First of all for a long time people have thought Linux not to be the target of malware. I would say that it has been a target and it has been for decades. I recall in the late 90s a Linux server at work was attacked, had a rootkit, IRC trojan and attack kit installed by script kiddies in Brazil. I think the nearest you can say is that desktop users aren't usually a target, which is mostly true. But with the share of desktop installs hitting a high recently we should expect that to change.

Second I think most windows antivirus products (including the built in one) are doing some active useful things. Most of these are not relevant on Linux (we generally don't run setup.exe from random websites). However! Here's where things get interesting. The rise of flatpak and other containerised applications. These I would say are very similar to setup.exe, and would make it trivial to embed malware into such a file. A Linux virus scanner could be checking these. Also we've seen direct attacks on distro repositories lately. I don't expect this to slow down. We are most certainly a target now.

Third, the other reason most Linux users don't use virus scanners is because they're usually technical people who would recognise (usually) something wrong and investigate/spot the malware. I would say two things are changing here. Simpler to install distros are bringing in less technical people to Linux and, the number of processes running on a machine doing effectively nothing in a desktop environment is way higher than it used to be. So technical people can be caught off guard. Also, a rootkit can hide all of these clues if done well.

So I would say there's a really good space to have a well made virus scanner/antivirus now. It is probably the right time for it.

To be more clear, antivirus in general are mostly scams because they are advertised to do much more than they are actually capable (especially proprietary ones that act as spyware such as Norton or Avast, which have been caught selling user data). Hash based antivirus solutions (such as ClamAV) aren't effective either because they rely on "badness enumeration", in which you try to determine all the bad samples (through a sample list(s)) and alert or delete them when detected. This isn't a good solution because a threat actor only has to add for example a single whitespace character into the code and it will produce a wildly different hash (which has not been sampled before). Badness enumeration is shit way to deal with real problems, much better is an allowlist approach, such as a permission system where to minimize the access given and soften the security until the app runs.

TLDR: Antivirus bad at job of stopping malware, and sandboxed apps good for security of your device.

I think you're missing the point that antivirus should kick in before the malware executes. It's far from 100%, but if you download something stupid, the antivirus should in most cases flag that before you even have a chance to execute it. In that case, you delete it, and the problem is solved, no need to reinstall or anything of the kind.

Of course the "real" solution is to be smart about what you install, but no one is perfect and we also can't expect the world to be super computer literate (unfortunately).

The "too niche" part is really weird to me. There's an estimated 2 billion PCs in use right now. ~3% of that are running some form of Desktop Linux OS, so roughly 60 million.

Incidentally, that's exactly the same number as the total number of Win95 licenses sold, and I can't recall Win95 being "too niche" for malware. Quite the opposite.