I can highly recommend you go even 'lower' than that and use something like Express, or go framework-less. I did that once, and I learned to appreciate so much more why Rails/Django/whatever is built the way it is. I really think I became a better Rails developer, and a better developer in general, by dropping down to a lower level.

Sinatra would be the Express equivalent for Ruby, and is very powerful and useful and illustrates these points. There is a lot more configuration with these types of things, but the tradeoff is the overhead that isn't bloating your stuff.

That, and I really think in hindsight the value of understanding things better and building 'from scratch' is immense.

Once I built my own 'CMS' using express and RethinkDB, I had to also set up on a templating system (so I chose React server-side). I ended up using a bunch of other tools or technologies as well. All of these were on my list, but I never really found a good excuse to look into them. But now I had to pick something (as opposed to settling for HAML in Rails, or any of the other 'popular' approaches, and actually figure out what the advantages and drawbacks were, as well as how to tie all these things together.

Not only was it fun in a way that building Rails sites often isn't anymore, it was incredibly educational.

I absolutely agree with this actually. Rails is a bit of a unicorn I think in that respect. You can create wildly amazing things without knowing much actual ruby at all, which is beautiful.