I swear I'm still totally clueless about this line of reasoning, and I'd really like it if someone could explain it to me.
In D&D, leveling is a mechanic to track the evolution of a PC's ability to survive and overall power. You didn't lose levels 1-2, they correspond to an stage in the life of an adventurer you're not interested to role-play. You don't lose levels 21-30 either, simply because a PC of 20th level in 5E will probably be more powerful than epic 4E anyway (at least they'll have rings of invisibility that they can actually use to, you know, become invisible...).
If one edition of D&D has fewer levels than the others, that is 4E, where the math and power of characters is developed in order to emulate the so called "sweet spot". Basically, your 30 levels of 4E adventuring are 10 levels of 3E stretched over 20 more "level-ups". If power level in 5E ends up similar to 3E, all you have to do is start at 4th level, make every character level up three times before gaining a level and there you have it: 30 levels of "sweet spot", your game will end before Wish has the chance to appear.
Obviously, you could still say: I don't care about all that stuff you're talking about, I'm focused in numbers, I want my character leveling often and I want to see that 27 in the sheet under "character level". If that's your case, you should be playing RC, where you have 6 more levels for your enjoyment. Even better, you could be playing 3E with the Epic Level Handbook, and suddenly you don't even have level caps anymore. What about a level 84 barbarian smashing puny 30 level 4E characters? Sounds like a lot of fun to me.
Cheers,