Hi there. Working on CMS design and integration since the beginning of PHP-Nuke.
With your list of requirements, you don't have many choices. I'm not sure about what "Do what Webflow can do" means... I suppose it's about creating databases (CMS/collections) and types of content (collections).
It's going to be Wordpress, Drupal or Joomla.
As weird as it is, Wordpress still is built as a blogging software, and you can extend it to make pretty much everything, but it quickly becomes quite a mess on the backend side, between types of contents, extensions, themes and sub themes, visual composer. With modern themes, you start with 4 different UIs minimum, only for the main backend and the theme. Cumbersome to say the least. There's room to develop your own extensions. There are a bunch of visual composers, all of them being very very far from what Webflow propose.
Joomla starts to be a bit outdated, but it has a developing crowd and fans. Known to be less powerful than Drupal but never worked with it really so...
Drupal is powerful, and a real CMS. And in its last iteration, version 8, it's not even a CMS anymore or just a CMS, it's a framework. Nothing is impossible and you design the front and the backend. Requires real coders. Learning curve is steep. Design and integration is the most ungrateful thing on earth (I did it from Drupal 4 to 7). You spend so much time on integration and browser bugs that you hardly have time and energy to add interactions, fine tune things etc. One thing that is revelatory: these days I noticed, Dupal developers tend to propose responsivity with... 2 levels. The very very super bare minimum. It's because it's not easy. When I design for Drupal (and I now stop after the production of HTML5, I don't do integration anymore), I build elastic layouts because I know that if I don't, the responsivity's going to be butchered, batched. By doing elastic at least there's little left to do for responsivity.
Ok so, we could have a debate on each and every point of your list. To me, with this list, you're closing doors before thinking about what the project can be.
If you like Webflow and try to find something similar, not only you're not likely to, but it's not going to happen before a while. Webflow is far from the competition. I understand why it's too limited for your projects, totally, I'm only talking about the experience.
Now there was a time when CMS were the go to solution... to make a site like Yelp for example. But this time has passed. The CMS we described here are PHP/SQL based, the old world. If I had to make a serious project for a serious scalable site meeting all of your reqs, I'll do it from scratch with modern tools like Node.js and a database like Mongo db (just an example). A real development. Like the Webflow team does... I guess they used React.js and a lot of other things. I used to say this is crazy to start out of a CMS, but I don't think that way any more.
For 10 years I was asked to design "in the tool direction". Now I use either Webflow or a mix of Webflow and the modern solution described above, and I design what I want, with tons of time left for fine tuning and interactions, UX analysis, A/B testing. And I NEVER have to debug anything regarding browser compatibility.