First off, the game is great. It’s great on its own merits, and it’s also great as a clear spiritual predecessor to Hades — which is a better game. They share so much blood: the core gameplay (which Hades does better, with more customization, depth, and overall snappiness); the commitment to aesthetic (which I actually think works better in Bastion, even if the craftsmanship of Hades is better). The flow of understanding a specific biome’s corpus of enemies, mastering them, and then getting pushed onto a new biome. The focus on ambient narration over cutscenes. It’s all there! 
It’s tough to like a work of art even as you recognize it as inferior to some later, more mature work of art. I think Bastion makes it easy. Bastion’s core plot and theme is beautiful and it succeeds on what it wants to do (you can even argue that Hades is a continuation of the same concept of escapism vs. acceptance!). Bastion is fun, even if it’s shallow. Bastion is short, and never outstays its welcome. 
Even if you have already played Hades, you should definitely play Bastion.