"modern gameplay" --- sounds like microtransactions - eq1 players are not about that life.
It could mean microtransactions, but doesn't have to. That said, EQ already has them, although they're mostly cosmetic/qol.
It could mean tighter game loop, faster gameplay, and so on. (e.g., Genshin Impact, while not strictly an MMO, has a 15-20 minute daily login time, which is too short for an MMO, but is indicative of something the market wants.)
If they have a lead designer whose head isn't glued to the past, they could sit down and distill what EQ is good at that other games don't spike on. The problem is a lot of those things aren't compatible with mass market, and if you're not doing mass market, why bother with this? As an exmaple, the old guild level PvPvE politics/logistical game prior to instanced raids was unique, but that doesn't scale, and isn't mass-market compatible. Insane farming/grinding was always EQ's thing, but if they want to go mass market, they probably have to drop that. Even outside mass market... let's be real, MQ2 wouldn't exist if the grinding wasn't nutty, which indicates it doesn't even work for a portion of the existing base. They'd need to basically eliminate MQ2's desire to exist, since MQ2 fixes/mitigates many of EQ's market-facing issues. Forced grouping - maybe ok. Blizzard's model with dungeon queues could work, if you don't consider spamming to find a group part of the core EQ experience.
So what's left? Personally, I think EQ's remaining market-feasible core attribute is relatively brutal dungeon clearing. Will we beat respawns? We're going to get a 10 pull if we don't do X, and we can handle at most 6-7. The relatively slow grindy gameplay in EQ can lead to sustained adrenaline sessions where if you're at the edge of where your group can be and you're racing something slow and impending that's creeping up on you. That doesn't really happen in Warcraft, as fights/encoutners are much shorter/defined (unless you're at the bleeding edge of mythic+).
IMO their success/failure here will be based on whether they recognize that the things much of EQ's
remaining player base considers core EQ (ridiculously grindy stuff) is not market feasible, and they focus on one of their other core strenghts. (The word remaining is highlighted because it doesn't include lapsed players and people that weren't sticky after tyring it prefer.)
EQ's caretakers, IMO, have never had a good understanding of big picture market stuff, so we'll see what they mean if/when they get closer to having a product. I wouldn't bet on it personally. But it isn't impossible.