What Happened To Custom ROMs?

I’ve been in the Android scene a little longer already. Maybe not as long as some others, but Android 4.0 was the first version I used. A lot of time has passed since then. But when I look back in time today, it strikes me that one thing that had found many followers at the time is no longer really important. Where are the Custom ROMs gone? When I got my first smartphone, I quickly realized what custom ROMs are and what they’re good for, but only after a while when I found out that I can root my phone without unlocking the bootloader and without losing my guarantee, I decided to try it myself.