Microsoft doesn't support IE11 anymore. You're probably safe to write modern JS unless you're in a very, very narrow niche.

That's not true https://docs.microsoft.com/en-us/lifecycle/faq/internet-expl...

And plenty of enterprises are still using it.

> And plenty of enterprises are still using it.

...but only as a back-up browser for those legacy internal web-applications. I’m sure all of them still install Chrome (or Chromium-Edge) for daily-browsing.

We sell into the NHS, and we still have high numbers of users on IE11 (and it's in our contract to support it). Chrome is definitely on the increase though.

Forbidding your developers from using arrow-functions such that you don’t need a JS build process can be justified.

Maybe a stupid question, but what kind of projects are ones where you don't need or want a build process?

Simple projects!

Projects where the client isn’t programmer-savvy and wants to make changes themselves and immediately upload them over FTP. Sites like self-hosted WordPress or hand-maintained static websites.

> Simple projects!

WP sites are far from simple. Maybe WordPress.com but definitely not the self host option. Not if you want anything other than a vanilla install.

> the client isn’t programmer-savvy > wants to make changes themselves and immediately upload them over FTP.

Why would you want a client who isn't savvy to make changes themself? Advocating for cowboy coding for end users is trolling... unless you're upselling a support package!? They can tweak things in the admin but I'd think long and hard before giving said client access to server files. Not to mention how easily end users mess things up by changing admin settings.

Having worked with such clients for 2 years, I gave up because at some point, the support burden was just too much!