Egg hatching is not fun anymore.
I don't think I'm ever buying coins for incubators again. Not until something changes, because I think Niantic screwed up big time moving cool & useful pokemon such as Exeggcute / Machop / Abra into the 2KM egg pool and leaving all the crappy ones in 5 KM eggs.
All I ever get lately is 5 KM eggs, it costs a lot of money to buy incubators for all of them and I just can't stand hatching another Psyduck or Tentacool or Whooper - these are crappy pokemon and I don't even need them, don't need that many candies either that comes from a 5 km hatch. It's not fun anymore! I'm completely unexcited to hatch a 5 km egg! Above all that 5 km is A LOT of walking for such a disappointing result.
I like 2 km and 10 km but both are super rare for me. And i.e. I desperately need Exeggcute candies but even with the mega rare exeggcute hatch from 2 KM - the amount of candies you get is less than rewarding.
Niantic needs to try and make hatches more exciting again, change the pokemon pool or sth because it's not fun anymore especially for high level players :((
Answers
Scythers, Kabutos and Onix come from 5 km too. But Paras and Krabby are a bane of mine. And imagine my frustration when I walked a 5 km (in the everlasting incubator, only one at that time) which turned out very old and so it gave me a Goldeen. The 'mon I already hated 'cos a few 2 km eggs had given me them. Lmao.
5km are both the most common and the worst return on investment and the occasional time a hatch an eevee and think will i finally be able to make a decent vaperon over 90% (i have caught over 1200 of the bastards and my best vape is 89% all the 6 95% that i have had all went jolteon mostly with bad movesets) I get it has certainly caught my attention, I haven't hatched a wonder since they came out of 10km eggs.
I regard hatching in general as a source of stardust with the potential of a nice surprise. Bad hatch? Ok, as expected, does not matter, next egg, thanks for the dust.
I regard hatching a 5km-egg as a neccessity to get free space for a new 10-km-egg.
I use incubators, to get 5km-eggs faster hatched away. Sometimes, even there may be a good surprise.
If hatching is so disappointing to you, there is no problem to walk some kilometers with an empty incubator.