I realize you probably won't believe this, but there is no reason your 3x8 shouldn't shift perfectly, if all the parameters are good, cables, housings, shifters, derailleurs , rd hanger not bent.
acera, alivio, it all works perfectly well if everything is good. We have a number of similar bikes in our household like this that just plain work perfectly.
I totally believe
djb , but I am one of the few impractical people who have spent actual money to
reduce the gear range of my hybrid bike for the sake of simplicity and a clean look, and I would even admit it was more for the latter (because Shimano Tourney 3X crankset is just ugly), so please just let me lead
pumpkinhed down the wrong path too.