edited the heading of the question. I think most of us here are reasoning why more people are not using firefox (because it was the initial question), but none of that explains why it's actively losing marketshare.

I don't agree ideologically with Firefox management and am somewhat of a semi-conservative (and my previous posts might testify to that), I think Firefox browser is absolutely amazing! It's beautiful and it just feels good. It has awesome features like containers. It's better for privacy than any mainstream browser out there (even counting Brave here) and it has great integration between PC and Phone. It's open-source (unlike Chrome) and it supports a good chunk of extensions you would need.

This was about PC, but I believe even for Mobiles it looks great and it allows features like extensions (and I hear desktop extensions are coming to firefox android?), it's just a great ecosystem and it's available everywhere unlike most FOSS softwares.

So why is Firefox's market share dying?

I mean, I have a few ideas why it might be, maybe correct me I guess?

1. Most people don't know how to use extensions well and how to use Firefox well. (Most of my friends in their 30's still live without ad blockers, so I don't think many are educated here)
2. It's just not as fast as Chrome or Brave. I can't deny this, but despite of this, I find it's worthy.
3. It's not the default.
4. Many features which are Google specific aren't supported.
5. Many websites are just not supporting firefox anymore (looking at you snapchat), but you would be right in saying this is the effect of Firefox losing it's market share not the cause (at least for now) and you would be right.

But what else?

I might take time (a lot of it) to get back at you, thanks for understanding.

occasionally I’ll find websites that don’t work 100% because they were coded primarily for chromium based browsers. FU Google