Yep. On my second run, I cleaned out the first level, and was able to upgrade everything and then skip past all of the other levels. Since the monsters get progressively more powerful on each level, skipping straight from level 1 to the end is the easy-mode strategy. Perhaps the full game could have some kind of key hidden on each level that’s needed to go to the next one.
Another change could be having the upgrade costs ramp up much, much more than they do now, but have resources worth much more on lower levels.