Your use of the word "shitty" here is highly subjective though. The evidence seems to be that most (or at very least a non-trivial subset of) consumers don't know, don't care or even actively prefer the "shitty" experience. Thus one could even argue that Samsung, far from being unaware or lazy is actively choosing this as the most rational and logical path to profits. It may just be that the people such as yourself are in the 10% of the population who are a) particularly sensitive to this sort of thing and b) extremely used to the iPhone level of experience.
Now I myself also find the stock Samsung experience incredibly ugly and laggy. The interesting thing is that you can remedy it in about 30 seconds by dragging a few widgets off the screen, disabling a few useless services and/or putting an alternative launcher on. Thus most of the lagginess is only "skin deep" and not a fundamental property of their phones. I think internally Samsung actually does very good engineering and optimization of their phones. At some point the marketing department gets a hold of the phone and completely ruins it, but thankfully it is too far down the chain for them to do any fundamental damage to it.