A LOT of classes have changed since then (even how the skills work/what they do).
They’ve completely changed combats, and how weapon/stats/defense/crit affect your damages.
You cannot open shops in town anymore to sell/buy stuff, only specific classes can do it (Alchemist, Enchanter, Appraiser, Pardoner, Squire…).
They’ve added A LOT of quests, so now you can level without even grinding if you hate that. If you like to grind, they increase the range of when you get good/decent exp, so it’s actually better to grind now.
So many things changed, and so much, honestly you better just check the devs’ patchs if you’re really curious about the before/after.
If you last played in CBT, most of the game has changed so you just have to discover a “new” game.
Unlocked’s “325 levels in 12h” was taken during a new player/exp boosting event, so only take his video with a huge grain of salt.
(Tbh I don’t even get why he posts it here since it doesn’t really help… Leveling in normal condition is much different than leveling when you get instances reset and exp boosts from events, obviously.)