Here comes another xpac where you need to be destruction or demonology to play competitively in any PVE content. The class designers have been missing the mark on locks since after WOTLK. I miss WOTLK where each spec had its own distinct unique flavor and play style and each spec actually was competitive. Metamorphosis was a ton of fun. I loved affliction warlock where shadow bolt filler between watching two dots…now its a game of whack a mole with multiple dots and you get punished if you miss any…what is fun about that? Who thought watching dots on 5 or 6 mobs was fun at all? Especially with a global CD between instant casts…affliction will never be good or fun. They should take a page from the mage re-design which has been hitting it out of the park. I got excited when I saw a potential come-back for shadow bolt play in the last TWW update, but instead we still have to use malefic rapture which is not fun, no one asked for it. I personally don’t know anyone who likes it.
Your in luck! WotLK classic happened for the last 2 years or so and hopefully you participated. Even more exciting news is that they’ve said in many blue posts and interviews that the warlock rework isn’t over yet, especially Affliction as they said it’s talent tree needs work.
Unfortunately the old design gameplay from the Wrath era doesn’t function well at all in the modern version of the game. Many content creators with Alpha access though have said that the Aff rework is doing good numbers and feels better-ish to play even before the devs have given it’s talents another good pass.
I would argue at least that Destruction has NEVER had a better expansion then Mists of Pandaria, so its not 100% true from my point of view that Wrath was the best design Warlock ever had. Not gonna dig into your other points, just here to be pedantic. 
Well we might see an affliction rework tomorrow. So far, there seems to have been a pattern or rotation. I believe over the last 5-6 weeks, it’s been:
Week 1- demo
Week 2 - destro
Week 3 - affliction
Week 4 - demo
Week 5 - destro
Week 6 - maybe affliction?
Not a Warlock main, but I really did enjoy Demo during WotLK. Probably the only time I’ve liked a caster!