All right, after reading the previous responses, I'm not original at all: GenerateBlocks + Kadence Blocks cover about 95% of my "page-building" needs. The remaining parts are done either with custom CSS or are gimmicks that I handcode myself.

I use the GeneratePress and Kadence themes (premium versions). I like the hooks (elements) in GeneratePress more than those in Kadence, but in my opinion Kadence has a much better header builder, so the theme choice depends on the type of project.

As for Elementor, WPBakery etc. - I can't stand them personally, opening a client site made with them makes my pulse go up... Working with GenerateBlocks is quite relaxing for me... I think it's the fastest way to build page layouts and it was THE plugin that actually convinced me to Gutenberg.

What I think might discourage some people is that sometimes the preview in the editing screen is not exactly what the page will look like, especially with more complex grids and nested stuff. Kind of close, but not WYSIWYG in 100%. I don't care about that, as I can imagine the final look based on the preview and block settings. I believe Elementor offers a better WYSIWYG experience for people who need it. But Elementor is just painfully slow and often I found myself wasting time looking for some setting and knowing that I could much more quickly write one line of CSS achieving the goal than finding the relevant button/setting in Elementor.

I remember the early days of Gutenberg when it was practically unusable for anything serious... It's impressive how much progress has been made in such a short time. Nowadays, I can't imagine WordPress without it.