In this form, there is much less wasted space and spells are no longer limited to three effects. But before we can load any database data, we need to transform the old data layout into the new one. This is not limited to spells, as almost every game system (including items, creatures, player characters, spawning, AI, and more) has had its database layout altered over the years.
Recently the new essence received from PvP which gives you access to an extra PvP talent, that also works in PvE situations, has made waves and there are plenty of threads about it on the forums. One in particular got a blue response which clarified just how powerful and how relevant the essence is supposed to be for PvE-focused players. Each spec gets a specific PvP talent added and some of them currently selected on the PTR are a little too powerful and feel mandatory for PvE, such as Moonkin Aura for Boomkins and Leader of the Pack for Feral Druids, but Blizzard clarified it is not their intention to have must-have talents for PvE available through the essence, as its primary goal is to add additional choice for PvP players.
That's not to say that everyone has an unrealistic vision of what vanilla WoW was like. There were already plenty of people on the WoW Classic forums pointing out that perceived bugs are just recreations of the original game. And as noted before, a flaw to one player is a key component of the original positive experience to another. WoW Classic will surely please plenty of purists in spades. But this goes to show that it won't be for everyone who has fond memories of the game circa 2006.