On my phone it often uses 100% CPU for extended periods of time, and does lots of writes to storage. And it has never been fast to begin with.
I mean, a five year old phone isn't top of the line anymore, but if other browsers work just fine, I'm reasonably sure where the blame lies...
Up until this point I always felt that there was no good Google free alternatives for chrome mobile browser, but this perception has definitely change now with the new Firefox Beta build.
I am switching to Firefox nightly for my default Android browser now.