[davemac8]

I think it's more likely that the low barrier to entry required to build a WP site is what has caused these issues, well, in the past, anyway.

What you are describing could be attributed to any poor quality code, it's not specifically WP core that is to blame, but rather poor quality code built on top of it.

In regards to managing WP sites being costly and taking up time, I manage many WP client sites and find the opposite to be true (I did write the code for all of them, though)