Is a progressive/completionist playstyle still feasable on main servers?

Good day! I had tried returning a couple of years back and there had been so many changes to the base game that it was very difficult to keep up with everything. I want to restrict myself, but if possible, I also want to avoid starting out on the classic servers. Anyhow, I had tried using the experience eliminator and had been working my way through as much of the older 1-25th level content that I possibly could. What’s greatly throwing me off, though, is that it seems that everything seems to scale down to my level. I was easily able to walk freely into any of the older areas at 10th level without risk. Also, outside of the single newer tutorial dungeon, none of the older 15-25th level dungeons were opening for me. I’m wondering if my progressive/completionist playing style is still reasonably feasible at all now? Or have things changed enough on the main servers that the experience eliminators are completely obsolete now?

I know of a group, but first you must solve my riddle if you dare.

Do not take the riddle from Mortignis. He is known far and wide as The Riddler and his riddles are fatal. Please, do not take the riddle.

I’m warning you.

I also returned recently to Warcraft after a long hiatus and have been working through the content in expansion order on a new character (aiming for the Loremaster achievement eventually). My strategy has been to leave the experience bar active, which has brought my character up to level 50 so far and made most of the mobs killable with one hit, so completing quests is fairly easy but I still get to experience them all. I no longer gain any XP from kills, though I do get a small amount from quests that will eventually bring my level up to 59. Once I reach Level 59, I plan to turn off experience and continue working through the expansions. You may want to turn your experience gain back on for a while to eliminate that problem. Just don’t let yourself go above 59 because then, as far as I’m aware, you will outlevel any content you need Chromie to access.

I didn’t realize that the mobs would start scaling once experience is turned off. Is this because Akadi is only level 13, or will this also happen to me when I turn off XP at level 59? More clarification would be helpful!