Mesa is literally the bottom of the barrel.
I recently jumped from flying rescue helicopters to the regionals here in the US. I work for an American Airlines wholly owned.
I'm earning about 80k USD or more in first year pay without taking into account the first year new hire bonus. The further up the seniority list you move the easier it is to make more money with the ability to drop sequences and load up your roster with OT as well as create rostering conflicts where they have to drop flying but you still get paid for it.
I'll upgrade as soon as I get my 1000 hours part 121 time which is not far away flying max hours per month.
Once upgrading the I'll be on over 100k USD as a captain.
I'll flow to mainline in about 4-5 years if I don't get picked up by another legacy first.
Regionals aren't that terrible anymore, obviously room for improvement but just don't go to a bottom feeder company like Mesa.