No reason why you shouldn't dig in compost. It improves soil structure, and it is a weak fertilizer. Sure, you can use it as mulch for moisture retention as well as weak fertilization, but if you're up to digging it in, that's the best way to use it. Bagged soil eventually loses its organic component, making it less friable.

If heavy clay soil is disturbed after a few years it is revitalized. I realized this from looking where holes are dug to access underground utilities as well as where they are trenched. Every spring a few days before I put new plants in pots I dump soil from pots into a bin,add fresh compost and complete fertilizer,stir daily then refill pots. It's a lot of work for a small return so one should weigh their priorities when spare time is limited.