I visually recognise websites I visit, app-like stuff especially.
Everyone using bootstrap has made the internet a mostly unrecognizable hogwash of same-looking stuff that I have a hard time telling apart, let alone any sort of lasting impression being left.
Think about it, even Bootstrap's page itself doesn't look like a default Boostrap template.
If the page has made no impression, doesn't that speak more about the content than the presentation? I agree on the visual aspects of being able to determine a page, but Bootstrap just provides a clean way to display some content, I'm alright with that.
And no, Bootstraps page doesn't look like a default template, but they don't say 'you must customise it', it's left up to the developer/designer/implementor.
I think that was OP's point though. Bootstrap is a framework, so please use it as a framework, not as a finished solution.
And I don't think lasting impressions are determined that much by content. I recognize pages by a sort of screenshot in my mind, it's a bit like recognizing faces. Happens too quickly for the content to come into play.
It's a finished solution and a framework, it can be picked on what you need from it. Not being trying obtuse, I just see a lot of criticism levelled at Bootstrap for creating similar looking pages, but for most of those pages they're primarily focussed around displaying content in a nice way (documentation for example).
That. Bootstap's site doesn't look like the default. Especially with the inclusion of colored images, that banner now and several other elements that most "built with bootstrap" sites lack.
Everyone using bootstrap has made the internet a mostly unrecognizable hogwash of same-looking stuff that I have a hard time telling apart, let alone any sort of lasting impression being left.
Think about it, even Bootstrap's page itself doesn't look like a default Boostrap template.