In the early game, I do not see any use for crushed stone. Notably no way to transform it back to stone/bricks. With the Muluna mod, a recipe to turn crushed stone into bricks is added, but locked behind Vulcanus.

In my game, this leads to a lack of stone/bricks because my only source is mining rocks or slag. It also lead to thousands and thousands of crushed stone sitting in chests waiting to be processed into landfill/slurry once the techs will be unlocked. Is it intended gameplay ?

In general, yes, but since there is a shortage of stone blocks, I will add a recipe similar to Muluna, but unlike her, it will give fewer stone blocks.

I will add this in the next update