All modern browsers have this.

Contemporary fonts have much less variance in the width of characters, except for a couple of outliers like the i. From there to a completely monospaced font is not as big a leap as you make it seem. For me, I'm fine with monospaced fonts for prose.

Also, the reduced character width (as a monospaced font inevitable has to be spaced at what the widest chatacters, such as w, require, means that you have to use a smaller font size to get the same amount of info per scroll/line/page whatever, again compromising readability.

Here's a comparison between the posted site, and the same site with the font size bumped up 4px, proportional (just browser default, I didn't cherry pick) and the ridiculously wide line spacing reduced.

Even with all that, the easier to read version is quite a bit more compact. Could likely bump the font size 2 more px and still be smaller.

https://i.imgur.com/DBFI2RU.png

I don't want say this in a way that comes off as insulting, but I'll just say it and please don't take it as a put down: if my kid came to me and expressed this much frustration and difficulty because of a sans sarif or monospaced font I would be concerned they had a problem with their vision or an issue processing what they saw, and I might research and/or take them to get checked out.

You probably just don't have a strong sense of aesthetics. Some people notice design-y stuff and some people don't. A lot of people do notice fonts, or misaligned margins, or whatever. And a lot of people don't. The latter category are probably never going to be good designers or artists or whatever. People are different.

What makes you think these proclivities about font choice are universal then? Maybe you are just insisting on what you find aesthetically appealing, while many people would equally validly feel the opposite?

There's an age-old debate of how much "good taste" is subjective, but in this particular case, it's someone hammering a nail in with a wrench. Some will be bothered, others not, but it's definitely the wrong tool for the job.

The example of not liking lights in certain places isn't a very good one. It's an attempt to elide all "things people don't like" into subjectivity, but there are actually things that are better and worse. You would agree that website design can be better or worse, right? And that some people would have a better eye for good or bad design? With me so far? I'm saying you're probably not one of the people out on the end of the spectrum that's best able to recognize good and bad in design, but I hope you recognize that good and bad design exist, and that people vary in their ability to recognize it.

    I think the inference that goes like 'if I can recognize something, there must be a corresponding faculty for that ability to recognize' is so remarkably bad that it is called a 'howler' in philosophy classes.

    Well lets consider it anyway.  Lets say you really are just the absolute best at having an aesthetic sense.  What is aesthetics?  It's knowing what looks good.  What does it mean to look good?  I means other people think it looks good too.  Ipso facto, having a sense of aesthetics must be extremely common, since whatever the largest group of people agree looks good is what 'looks good' to people.  So congratulations on your very common ability I guess.

    Or maybe you are more of a snob, and your aesthetic sense is so rarified other people can't even begin to appreciate the things you think look good or bad.  Lots of things you think are very beautiful would be called ugly by the vast majority of people, and what you think is ugly might generally be considered beautiful.  Nobody understands other than the other elite aesthetes, which you recognize because they agree with your judgements.  I could say something snide about how everyone has some group of people that agree with their judgements, and all that makes one group or another elite is that they say they are, but I'll just say congratulations, and point you in the direction of a modern art museum.

Not to make it personal, but if you are going to claim some kind of innate design ability, you should remove the link to your website from your profile.