https://gs.statcounter.com/browser-market-share Unless you're targeting some really niche market people will have a relatively up2date browser. It's not a problem to use recent features once they've been implemented by Chrome and Safari.
If you want to serve content to human people and not just to eyes or wallets then at least be aware that most modern browser share statistics collected with JS don't reflect the reality you'd see in your webserver logs.
I don't think the demographic is realistically relevant.
Of humans that deliberately disable JS, certainly going to be under 0.1%. (I’m one of them, incidentally, because on average it makes the web much better, lighter and faster.)
Of humans where various JS doesn’t run, due to having an older browser, a corporate proxy that blocks some things, a content blocker like uBlock Origin that incidentally blats your script, unreliable network conditions, and more things… well, that number is regularly quite a lot higher than 0.1%, often above 1%.
As for something like the Statcounter tracker, which these specific stats are built from, their methodology is obviously stupidly broken and has been for many years: ad blockers will tend to block it. (uBlock Origin does by default, and I expect others to as well.) And that number is generally agreed to be well above 10% (some say as high as 40%, though I’m sceptical of that), and heavily overrepresents users of less common browsers like Firefox.
97.23% of internet users do not care.
If you are arguing to not use Working Draft mechanisms in production environments (and you probably are), yes you have a point. Better safe than sorry, it's called a Working Draft for a reason.
But if you are arguing to not use something because Firefox (and only Firefox) does not support it, you are going to have a fun time trying to convince most webdevs to care about just 2.77% of all internet users.
You're essentially saying "I want to use this months old API, and fuck you if you still have a browser from last year." People used to respect some amount of backward compatibility.
There's no reason to "respect" backwards compatibility in an inherently online product that auto-updates.
There's nothing ideological here, it's just about being practical.
So users in that situation should not be punished by web devs who only support the bleeding edge browser versions.
When 90% of users are on the newest version within a couple weeks, that's not "bleeding edge". It's mainstream.
You're also opening yourself up to security vulnerabilities as you browse.
If you turn off auto update, it's up to you to accept the consequences of both security risks and of sites breaking.
you say that like I am the only person who does this.
> When 90% of users are on the newest version within a couple weeks, that's not "bleeding edge".
[citation needed]
Essentially, yes: https://caniuse.com/usage-table
And neither Firefox nor Chrome self-updated beyond a certain point on my few years old Android tablet, which is still generally very usable for browsing and YouTube.
And the browser on one of my phones stopped updating, once the OS stopped getting upgrades, for about 2 years before I stopped using that phone (because there was nothing as good as it to upgrade to).
Non-latest browsers are a small percentage of users, but it's a myth some site designers believe that all Chrome, Firefox and Safari installs auto-update to latest versions except where the user decided for themselves to block updates.
To the owner of devices in generally great shape, that work fine with alnost all sites, sites designed with the bleeding-edge assunption can feel a bit "unnecessarily buy a new version of the exact same electronics with your copious spare cash and litter some e-waste landfill to view our content today!".
Site designer's choice of course.
But it's a myth that the current mainstrean browsers stay up to date by default for everyone who doesn't disable it. Some users can't update. This should particularly be in the awareness of designers wanting sites to be readable by people without much disposable income, or some accessibility issues.
But in this day and age of browsers being Chrome and Chrome and Chrome and Chrome and Safari, all with forced autoupdates, there's little practical weight behind "browser <X> doesn't support it!". If Chrome supports it, the internet supports it whether any of us like it or not.