What is wrong with this simplification.

I think there is nothing wrong with the second one. Both can be correct. For me, neither is easier or harder to read.

If you want to ruffle some feathers, consider all those 16th notes followed by a 32nd rest. Change the 16ths to dotted 16th and make them staccato. Even easier to read. Depending on the tempo, the result would be the same. Most people will disagree. It depends on what your goal is. Most people will tell you to stick to the original. But if it is for yourself, you get to choose.

For playback in MuseScore, I will sometimes use the original style because for some wind and string instruments, staccato isn't short enough. Probably more information than you are interested in.

The first example is more consistent because it uses 2 voices in the right hand all the time. While in the second example there is a mixture of the use of one and two voices. But I don't think there's anything really wrong with the second example, it's more a matter of preference. In music with a predominantly polyphonic texture, the first example is preferred.

This is from Grøndahl's Etude de Concert, Opus 11 No. 3, measures 14 and 15. Nothing is wrong with your version, except for the mistake in measure 15 where you have what looks like a quarter note in there. But, in the original version I think the intent was to differentiate the two voices in the top staff. If you don't care about that then by all means combine the two voices into one. It won't present any problem since this is a work for piano. They had to do that in older scores. We don't have to do that unless one of the voices has to be played more prominently. The original score doesn't mention anything like that, so do whatever you think if it makes it easier to play. Good luck!