Bootstrap is good if you don't have a lot of time or budget to spend on design. It makes your site look ok with minimal effort but usually your result looks similar to someone else's. I don't consider that a problem.
The more time and resources you spend and the better the people spending that time are, the better your result will be. Bootstrap, like a vanilla wordpress theme works even with very limited effort, but obviously it's not ideal and it looks like everything else.
If you've got a great designer spending 100 hours on a theme, the result will be much better. He might use bootstrap or something else or nothing. The more time and resources are spent, the less the defaults of the framework impact on the final result.
Comparing Bootstrap with 5 hours of work from someone who isn't great at design to non bootstrap with 50 hours of work from someone who is great at design isn't a useful comparison.
That is why the OP mentioned "Bootstrap is good if you don't have a lot of time or budget to spend on design."
Maybe you should have posted in the root of the thread, instead?
I meant that you can spend a lot of time working with bootstrap and get good results too. This is actually pretty common.