It's like a banana (custardy) and is probably similar to figs in that they don't store long. Figs are double annoying as they have to be picked when ripe and then are only good for like a day. The ones at a grocery store are picked too early and thus nasty. Like a flavorless peach. Pawpaws also are supposedly carcinogenic and require 2 trees to fruit iirc.

If it's hard to buy, there's a reason such as: 1.) Not good to eat, 2.) Can't be grown economically due to slow growth or expensive inputs, 3.) Can't be stored for long, 4.) Superior substitutes exist (possibly mango or banana), 5.) Illegal nature...etc.

Edit:

After reading, it confirms the inability to store and need to pick on the tree (similar to figs). I have a feeling that the recently coveted nature of the pawpaw is just that people want to try it once and not a sustained need like apples. I didn't see any mentioning of them being carcinogenic though. Maybe I remembered that wrong? I do see that it has annonacin which is also pretty bad if consumed regularly (hard to do with pawpaw) and something that pregnant women should probably avoid.