Interesting thread.
The first thing a bass amp has to do is work all the time and not fail on the gig. So, there is that. If anything, through my playing years, amps have given me the most heartburn on the gig of any piece of gear.
The good thing now is that we have a LOT of really outstanding amps to choose from. We all argue about the various differences; but, really, I can get good workable tone from most amps out there.
The micros are flat out amazing. They just keep getting better. From a practical load in / get the gig done / load out at 2AM basis, not much beats them. I would not be without one.
But, I also happen to think that a high quality preamp is very important. Here I am talking Demeter, Alembic, etc; whichever flavor floats your boat. Those have not changed in decades. What has changed is the weight of the power amp technology (related to micros). A player can now have, for example, a Demeter and a Crest ProLite in a rack, which weighs in at less than 25 pounds. That's amazing.
So, for my purposes, a solid micro and a solid rack get most jobs done. I still love the big tube amps; and if someone wants to set up an SVT for me as a backline, I never complain about it.