I think they're all just super useful to have in a world where 2/3rds consists of water even if you predominantly live on the land. Note that there is no driving force behind any of this other than dumb selection and mutation and that it would be very strange to first lose all this stuff upon emerging from the sea but still living predominantly in coastal areas (as we still do today!) and then to re-acquire those traits over a relatively short period of time because suddenly they are pre-requisites for survival. Much easier to take them along for the ride where they are handy all the time, as evidenced by many other mammals that have all of these (and sometimes more).

But you're right in that in theory it could have happened and like any essentially unfalsifiable theory it will likely remain that way.

It's funny because depending on which field we're looking at I probably have my own 'aquatic apes' based on how solid I think a particular theory is but without dedicating a lifetime to it I'll just take the easy way out and align with the largest body of scientists until there is hard proof to the contrary. But in some fields the theories are known to be broken and then such discussions get a lot more interesting.

None of those are out of place.

aquatic animals (otters, beavers, could go on) have plenty of hair. Our lack of hair is function of avoiding parasites using our brain to protect our skin instead of fur armor.

All mammals have fat so I'm not going to get into that one.

All mamals have a swimming reflex, except even though most of them are not aquatic, their reflex actually works. humans that dont spend a long time to learn how to swim ... drown.

but there are features that are very much against us being aquatic: shellfish and fish allergies.