That which works is sufficient evidence unto itself. The whole idea that what is beyond the capabilities of reason doesn't exist is laughable, except when it becomes inhuman.

I'm not sure if you're using the strict philosophical definition of rationalist or not (the "requiring evidence" phrasing makes me think not -- that would apply to empiricists, not that they're mutually exclusive though they were at odds in the past). If you are, I'd suggest that the body of early Buddhist work contains lines of thought that aren't dissimilar from Plato who was most definitely a rationalist.

If you're using the term in a more general sense, then social science provides evidence for the efficacy of various Buddhist practices (e.g. mindfulness). I know the state of affairs in the social sciences are suboptimal (e.g. the replication crisis) but it's the body of knowledge we have to work with now.

At this point no one may even read this, however I’d like to get it off of my chest. Philosophy, the fundamental study of reason, existence, knowledge, values, etc., has been around a very long time and yet is still more valuable to us an individuals and in a society then it has ever been. Religion is a lovely and long studies framework for studying those philosophical principles. It’s not the only framework but it is an exceptionally accessible framework to use.

Philosophy does not require evidence. Philosophy does not require justification. In fact at times it’s best to remove those from your philosophical thought experiments in order to better understand some principle or thought.

Rationalism as a philosophy isn’t without its faults. And many lovely arguments have been made around it. Keep that in mind.