I use Firefox since it was Phoenix, back on my Windows 2003 and except there was time when it was noticeable slow so I was forced to use Chrome/IE I hardly can

I use Firefox since it was Phoenix, back on my Windows 2003 and except there was time when it was noticeable slow so I was forced to use Chrome/IE I hardly can find things to complain about regarding changes. I see other people complain a lot, which makes me think I'm missing some big part/have some unusual usage for Firefox. Any hints what I may be missing/doing strange way?