You don't need to justify yourself.
Thanks, that's actually reassuring to hear.
I'm subbed because i do mainly endgame stuff and sometimes Low Level bg... and now can anyone tell me why the heck i should make 20s instead of 29s? On 29 we have more abilitys more dungeons one more Talent and more usage of professions! Here is literally no reason to Play a 20 instead of 29....
All four of these levels
can compete with each other rather well and I assume even more so in Dragonflight due to the new Talent system giving us all so many important abilities that we can pick-and-choose as we please.
The only benefits that being a higher level will give you is that you might have a few baseline abilities that lower levels do not have as well as having a few more talent points to spend.
Level 20 - Free to Play / Vet - The perks of playing at this level are simple; You can play the game for free.
Level 25 - ex-60, Classic Level Cap - Mostly for people who have an old level 25 character with gf'd gear. There's no need to level up that character. In fact, keeping it at that level might be interesting for a "Classic plus" experience, and it makes any rare/unobtainable item that you may have worth just so much more because it's not on a "dead character level" (which is the main reason for playing a lower level).
Level 27 - ex-70, TBC Level Cap - Same as above, but for people who have old 27s.
Level 29 - Bracket level Cap - You'll have the biggest advantage over others at this level; The most abilities, The most talent points and possibly access to some items lower levels cannot get due to zone and dungeon minimum level requirements.
I'd still like to reiterate that
a level 20 IS able to compete with 29s. Yes, you are weaker. Yes, the 29s have a big advantage, but no it's not an "instant-loss" situation.