It's true that Random Number Generators as thresholds to get stuff that helps-defeat the "R.N.G( 's) ." later feel like a 1-time steep climb. Thresholds can be rough.
I try to have fun when being repeatedly-defeated by this Game Mechanic by enjoying the other ones, sometimes even while-attempting to get-to the next "'loot' 'box'" ("banned" in at least one "country" - or more? - now! [would this apply to MC..?]), sometimes not. So for example, we used to have to get Melon Seeds from AbMS Chests (I don't think it was Dungeons, but maybe), and often Pumpkin Seeds as well (if we just couldn't find Pumpkin patches on the Surface).
I'd make a point of just Fighting everything - get better at that - using Water Flows to move-Hostiles away, Build more-and-better, and even entertain thoughts of TNT (which might destroy Spawners) but mostly Lava. But often I couldn't find an AbMS, and /or going-through it to find - such - Chests, which might or Might Not contain such was Not going to give a soon /favorable result.
Which's why I'd do all-But that, at other times. I wouldn't make anything hinge - my sense of anything like "forward" "Progress" in a Game - on any one thing (heck, otherwise I might enjoy Hardcore more [on the flip side, ever heard of "Progress Quest"?]).