I use bootstrap because a common design language is a good thing. If your iOS app uses custom controls and deviates from the Apple design language, your design is rightly criticized.

Yet on the web, you are criticized for not being different.

I call B.S.

I don't have to teach my users what a hamburger menu is because they've seen it elsewhere.

My users think my sites look good because I let professional designers do the heavy lifting. Because my sites look like many other sites, they are comfortable, easy to use and not jarring.

The only people who care that you've used Bootstrap are other web developers. And it's probably not because everything looks the same, it's because you did it the easy way. You're supposed to walk up the hill backwards in the snow both ways like all the old-timers did.

Guess what, your clients want you to do it the easy way. The quicker you get the design done, the quicker you can move on to other things that add value to the site.