After a bunch more plays:
It's very easy to lose in the first few stages if you are aggressively trying to spec towards a winning strategy - seemingly if you don't do this your runs almost never end in success. Once I got the snowball going (usually, gold mine > walky talky > salamander & campsite > 0 cost pips > wrench) it was quite easy to win.
This leads to a high level of difficulty that is driven more by randomness and less by player choices. If you had a more certain path to a given build it might feel better for players, even if the game were made more difficult numbers-wise.