Bat guano has been used as fertilizer for longer than history goes back. The Spanish enslaved Peruvians to harvest guano to export to Europe in the 1700's.
For sure making and mixing your own soil mix will be better and cheaper than buying a bunch of bagged up who knows what.
For me, the most fun and enjoyable part of growing with soil, is making the compost that goes into my mix.
And I have no doubt that the influence really nice compost has on the final product is huge.
If you plan to use quite a bit of super soil, it's worth the time scoping around for a local sorce of high quality manure and forage (alfalfa, straw, grass clippings) to mix up and compost.
Instead of buying bags of potting mix for a base, I just use a combination of home made compost, worm castings and leaf mold. I then add the mineral amendments, alfalfa pellets and let it cook again.
The end result is much better than super soil made with peat or coco based potting mixes. And much cheaper/more sustainable/more organic.
But, you need the room and time to make large amounts of compost.