We have a list updated quarterly based on browsers with 5%+ market share that is baked into any requirements that clients sign off on, with additional time/money required for supporting anything outside of the list.
Saved our bacon many times when it turns out the client is using a 9 year old Firefox browser they refuse to upgrade, or it turns out one particular branch office is still stuck on IE8 (true stories...)
For development purposes I use Chrome for work stuff and Opera for personal projects.
Then, using your analytics package (which you have, correct?) You run testing either on actual hardware, or something like Browserstack for everything else in descending order of popularity by unique visitor.
Really, you have several different rendering engines and JS engines in play at any given time - and it's helpful to have an agreed upon support model in place prior to starting development. Generally speaking, support anything with 5+% in the past 90, and make a argument for not spending time supporting things below that without very good cause.
Cross-browser testing is hell and responsive has made everything multiple times worse for the amount of manual grunt work that has to go into every non-trivial custom web project. Greatly envy non-web developers who can build an interface once and it's done.
Also, cross-browser compatibility is important to me, and I figure all my colleagues test stuff in Chrome and will complain about stuff that doesn't work there. I can't tell you how many Firefox-specific bugs I've found in our site.
The tough part is finding someone who will regularly check stuff out in IE or Edge, if you don't want to be spinning VMs up and down all day every day.
I did find this article[1] on using chrome and workspaces as an IDE of sorts. I think its kinda nifty.
https://y6326.wordpress.com/2016/02/17/basic-setup-chrome-de...