Here's some thoughts:
I run a custom system right now, and my current analog crossover is an old ATC model from 1982. I have not serviced it, and it's full of old capacitors and op-amps that might be considered sub-optimal today.
The system sounds excellent and has tons of resolution, and the driver integration is perfect!
Even if I'm eventually going to clean up & service the crossover (and I'm sure I'll squeeze even more information from the system by doing this), this tells me that the correct slopes are far more important in crossovers than principles.
Of course, it all adds up and the pros and cons must be weighed.
Once I've completed servicing the current crossover I use, I'm going to try out something completely different. A line-level passive crossover, L's and C's, just to see how far I can get with it.