Blue
Ravenous Bugblatter Beast of Traal
3.) Along the same lines with my first two quirks, the biggest problem I have with the character classes is that everyone is a superhero. That Fighter that went out on his first adventure in 1E was the farmer's kid that was striking out to make a name for himself. He started out weak and through levels and magic items he gained that power. Through adventuring he grew and made a name for himself. He came back to town as the victorious adventurer. In 5E the level 1 character might be a little weak but the super fast progressions ensures that he is a level 3 superhero in no time.
I heard you on the other ones, but this one seems off. A medium encounter @ 1st level has an XP budget of 50XP per PC. But that's not actually 50XP earned each, that's after the difficulty modifier - x2 for 3-6 monsters, a common place. So it's 25XP per PC per encounter. 300XP is 12 encounters.
For us, that's about two encounters a night, and we play every other week. So it's about 12 weeks to get from 1st to 2nd. Sure, some encounters are tougher and grant more XP, but not every session has two encounters, so it evens out.
The point before had the DM controlling the speed of power creep by the rate of giving out items. If your table finds it to fast do the same, control the speed of leveling to be happy for your table.