I was building a concrete house, and I needed to move my staircase by one block, but I noticed that it was taking a long time to mine and wasn't dropping anything. Looking at the jar, the loot tables are correct, so I looked at the jar for Create, and they have a json in data/ minecraft/ tags/ blocks/ mineable called pickaxe.json that includes all blocks breakable with a pickaxe. Adding the following to that json fixed the issue.
{ "replace": false, "values": [ "#moreconcrete:walls", "#moreconcrete:stairs", "#moreconcrete:slabs", "#moreconcrete:pressure_plates", "#moreconcrete:levers", "#moreconcrete:fences", "#moreconcrete:fence_gates" ] }
I wasn't quite sure how to make a push request for this, sorry. I'm still new to github.

Thanks for your report!
The initial version of this mod was created on version 1.16.5 while the mineable tag system got introduced in 1.17, and I must've forgotten to add the tag during the porting process. Easy fix on my end, will release a patch for both 1.17.1 and 1.18.1 ASAP.