I don't know about more obscure but I've frequently used Foundation and like it. It doesn't feel as bloated at Bootstrap. I haven't used Bootstrap in awhile, so maybe it's gotten better, but I always felt like the number of elements required even for a simple modal seemed like overkill.
You are definitely not the only one who has not found Redux "easy to reason about". I think the concepts are somewhat straightforward, but in practice are a little harder to grasp, especially in real world applications.
I do a lot of Wordpress development as well and I'm not a huge fan. This GitHub repo has a long list of flat file CMS options:https://github.com/ahadb/flat-file-cms
I've used Kirby and found it to be pretty intuitive if you have a custom design. The thing that is lacking from these other options is a lot of theme options which Wordpress has a plethora of. Often my clients don't have the budget for a full fledged design and there are plenty of Wordpress themes out there which make it easy to have a decent looking website (mobile responsive, custom fonts, intuitive layout, etc). Hope that helps.
Couldn't agree with this more. I wrote a blog post about my frustrations with Redux and he took the time to not only respond to my post but spent an hour with me on Skype helping me figure out the issues with my application. Really awesome guy.