The only reason to play Classic is 100% nostalgia, in my opinion. The game is solid, and I believe its better as a game than BfA, but all the changes WoW has had over the years were for a reason. People noticed what sucked, and asked for changes. Blizz just went too far in some cases. =)
The one little issue that had made me start thinking "wtf am I doing playing this?" has been the spawn timers / rng quest drops. I've played both Horde (troll shaman) and Alliance (nelf hunter) to lvl12 on Ashkandi (fuck queues). The spawn timers seem to range from 10sec to 10min (with Menelas in Teldrassil being like an hour). Its stupid. Then you have the rng aspect of getting the quest item you needed off the mob. Even more stupid. If I need a tiger skin off a tiger I just killed... why don't I get it? Didn't care for that at release, and still do not care for it now.
I never played a Hunter until Legion, so playing a Hunter in Classic is something of a shock, lol. Have to buy ammo.. wut? Quiver taking up valuable bag space.. wut? I did the taming quests, and I'm guessing each of those pets are only temporary until you get the taming skill by default, since they each disappeared after a time. Funny stuff, not sure I want to deal with that, so back to then shitty horde side for Shaman fun. Money from questing / killing in Teldrassil seems way, way, way better than Horde starter area.
Edit: Speaking of afk. How long can you afk? I left my character online while I was at work, but it was disconnected when I got home. Was there a server restart yesterday between 8am-5pm? Or is there an autokick if you have no way of making the character do something every few minutes?