Remember: IE6 was the best browser for a while, the problem was it did things slightly different and people targeted IE instead of the web, exactly as they target Chrome instead of the web today.
IE6 was a broken implementation of the standards of the time.
And Microsoft decided that web browsing was done and did not update their browser.
It was a scheme for vendor lock-in.
My career started in the IE 6 era and even then people tested in at least 2 browsers.
At most I’ve been lucky to have 1 team member who cares about this stuff. Maybe other companies are better but this is my experience the past 5 years or so.
I don't think many web developers who have really lived through the IE 'glory days' would say the current situation is even nearly as bad.
Do test in Firefox (and Safari). If it works in FF it mostly works everywhere, but Safari has some quirks I think.
In fact as long as I test my code in Firefox I haven't been caught with something that didn't work in all browsers any of my customers supported the last 4 or so years.
There are a few Chrome-specific things one shpuld
Mozilla has a habit of taking a decent, slimmed down browser (Phoenix, for those who remember that era), adopting it as their primary because their previous became a bloated mess... then taking the new fork, making it unwieldy and forcing people to create yet another fork to reign it in.
Tell me again how this is Google's fault.
They simply made a better browser.
Chrome was better for me for about 15 min until it crippled uBlock origin - at the same moment Chrome took action against non-Google advertisers, that Google didn't like.
Meanwhile my memory issues with Ffx decreased while Chrome's grew; I've no memory issues to speak of at all now. Ultimately, FFx plugins wound up helping craft a positive browsing experience on Ffx, that can't really be duplicated in Chrome.
Now I use Chrome to open up a single, overseas website because their native translation really is the best. Firefox (95%), Opera, Brave even Edge all see more use, however.
Please don't rewrite history with things that aren't true - Chrome was significantly better browser for a long time with significantly better developer tools which made tech people prefer it early.
But chrome did the impossible, they shifted the Moms and Pops and most unbelievable, the absolute holy grail, the corporate desktop.