as someone who rarely gets beyond the intro level of "seated" games for exactly that reason, undertale is super easy to pick up and play a big chunk and come back to later.
There's an element of 'get good' to some of the puzzles but honestly if you are good at the gameplay, you can bust through a playthrough in like 5 hours
....belated realization: should that have been "a low time/effort spent to content experienced ratio"whichever one has more content