It's impossible to say one era is more charismatic than another cos it simply isn't true... WWE has just as many charismatic guys today as it had in Hogan's era or the Attitude era but there is a difference in what WWE does with that charisma now than it did then.
I've read a lot of answers here and no one has come up with the reality. Wrestling in the earlier eras, even WWE was a LIVE EVENT business. It was about "bums on seats love" and TV and PPV was a vehicle to drive that. Guys got time to practice talking cos they had to do endless pretapes for each town to sell the live shows...guys would spend whole days literally doing the same 2 or 3 promos with different town names in there. So it was impossible not to get better at talking over time, some would then be able to zing it off the top of their head or have 9 or 10 promos. Even the top guys rotated them out...
Every WWE show back then had promos interwoven... not in the ring for 20 minutes, but 1-2 minutes with Mean Gene or the like, live sometimes and others pretape... Last night for example, where was a Miz/Mizdow promo? You're telling me they couldn't cut Rock and Co down by 2 minutes to allow one? But WWE isn't looking for those now.
Think Randy Savage was a "great" off the top guy? No, he used the same "Don't bet against the Macho Man" at every Royal Rumble for example... like his costumes, he kept track of what he said and where so that his 10-15 promos never got trotted out in the same place twice or too often and that helped build his credibility. The Rumble would begin with nearly 30 promos of how they were going to win...some were awful and you'd see why you didn't hear them often... SNME used to have the same multiple promo opening... those promos were always about more asses in the arena to make more money... so it mattered.
Then it became a TV show first and live event business almost as a sundry.
Now it's about timing the show for TV first, popping a rating, getting social media share or schilling something... anything but selling the arena out. Those pre-tapes aren't there anymore, no 2-3 days with Pat Patterson etc overseeing and helping guys... now it's all done in the Performance Centre, sure you can go and cut a promo in a room as often as you want... but it's not the same, there isn't that pressure there... if you're not a "talker" now chances are you're there for some other reason anyway and it doesn't matter... Also the current trainers are not exactly known for "talking". Albert, Billy Gunn... not really... All Gunn ever really did was tell people to Suck it... Regal and Duthty...sure but they are not doing the day to day training, they are the "higher ups".... I am hoping Goldust soon makes that move down to NXT, cos that's what it needs...someone who is a A+ mic player hands on day-in and day out down there.
At the end of the day, back then you absolutely HAD to be able to do it all just to get hired into a territory, much less WWE. Now WWE will sign guys to a lower deal for a year with a "if it works, it works" approach.. for every Bray Wyatt who comes along there is at least 3 Braden Walker types... Territory promoters were not gonna "take a punt on a kid", cos there was too much at stake... thus WWE didn't either, arguably Nash was the first time they did and Trips the second... nearly everyone else signed until Rocky and Mark Henry in 1996 had some kind of pedigree in the business.
Remember as well WWE was helping its guys (or hindering) by ensuring everyone had not only a gimmick but everything from logos, to music to merch back then... Remember those old sticker books/toys that would have a logo for each guy on them? Like Mr Perfect's column type writing or Macho Man's "Madness" scrawl... Even down to the colour of the costumes WWE was controlling those aspects. Now they don't... they have gimmicks but Rusev doesn't come out in Volkoff style hat... he dresses like an Olympic athlete would... someone like Ambrose, simple jeans and vest, how many guys wear standard trunks now? most of the roster...
Guys got over back then because that package worked... Brutus had the bizzare holed tights with fishnet and bowtie/jacket, he looked goofy but it fit his character. Big Bossman had the "police uniform" that later became the SWAT uniform and then the Shield look... it's pretty generic for a lot of guys now to wear camo or combats. Rick fricking Rude.... custom tights made and paid for himself for every PPV or big match.... the tights didn't get him over, but it was the "final piece" of the package and played into his already big charisma factor.
Only a few, like Chris Jericho with his light Jacket or Finn Balor actually make any effort to wear anything but their latest merch or baby oil to the ring. Miz has made some effort over the years, so has Cody and Bray but in general very few guys get the "whole package" concept to the level even the 90's and 2000's guys did, much less the 80's... Reigns looks awful in that SWAT vest, and it hurts him... it's harder to take his charisma and promos seriously cos he's the kind of guy who should be ripped and no top of any kind... he's clearly not as defined as others and can't get that way...so he uses the vest as ironically a shield...
So there is a lot of that in play here... You can't say guys like a Titus or Slater are not charismatic, they are... but WWE just isn't interested in them for that...if they were around 25 years ago, both would be higher up the card for sure like Rick Martel and Bad News Brown were...