I will just comment from the idle game prospective. For a long time, speed gives so much (almost 3% gains increase per point) that its not worth putting points into anything else. Even at half as good as it is, it would still be a good candidate to put points into. You have to think about the balance and % gains per point added so it makes sense to use multiple categories. As for the items, the multiplier amounts are so high and new things to buy make the old ones so inferior that they are not used. Part of the idle games is also item balance so people have to thing (if just a little bit) on what to buy and what stats to put in.
if you lose you can still move on! I purposely lost constantly to get to the last level. on the last level I filled it with archers, won, and it was the same exact screen as losing only I had 3 stars.
 "IdleByte"){kind=icon}
 "Siege Knight"){kind=icon}
 "Corporation Inc."){kind=icon}
 "Alchemist 2"){kind=icon}
"Oops." - Our programmer's last words. (fixed it so you have to win to proceed now)