Microsoft doesn't have a browser today, it's just a repackaged Chrome supporting the same Blink monopoly.

I am honestly surprised Firefox on Windows is slow for you. I don't personally use Windows, but many on here say it works well there since v57.

For what it's worth I don't experience slow loading with Firefox on Windows, or any notable slowdown in any way.

Start Firefox in the Profile selector and try using a fresh new profile. Or start in safe mode. Some old, forgotten configuration or addons are sometimes the cause. For example a privacy-enhancing addon CleanURLs disables ETag functionality by default. So all sites using ETag for caching content won't be cached. Big loss.

Is this still true in Firefox >= 57?

In my experience FF is not behind chrome with new features. It's usually on par, or even better. Sure safari is annoying. But the developer tools in firefox are alright. I even find them better when it comes to debugging css stuff.

It's odd that you mention how Chrome needs competition but also decry lack of features in other browsers. That is one of the ways they are attempting to monopolize the space.

The standards are meant to be agreed upon by several parties, including both Google and Mozilla. Google implements new features in order to control the way they work, instead of allowing input by all the parties involved. It's always faster for one company to just do whatever they want than for a group of organizations to come to an agreement on what to do. The slower way results in better and more equitable implementation for everyone though.

Why do you say so with such certainty, though? I find it nearly impossible that you never saw someone claiming the opposite. There's even such a response to your own comment so clearly this experience is not universal.