In fairness to younger gamers, I find many old RPGs hard to get into now too. It's not graphics. It's not GUI. It's just I've seen it all before, as far as fantasy goes. Tolkien was the peak of fantasy; no game has ever captured the genre to the degree he made it, or to the degree Peter Jackson's film adaptations manifested it as cinema, and *generic fantasy setting #4055* can be laboriously dull by comparison. They rely on the afterglow of Tolkien, adding no life of their own. It's a lot to expect people to invest 40-80 hours into, when you realise there is nothing profound behind the wood housing that evokes the master's superior work. Many RPGs were not worth it back then, in the 1990s, either. It's just we didn't know better, and stuck with things thinking they would improve, as kids, with spare time, lacking experience in how commercial entertainment often wastes your time. Like 'prestige' television that drags 6 episodes worth of material across 6 seasons, RPGs overstay their welcome easily if they don't make their case quickly, and keep making it therein. We are wise to the JJ Abrams 'mystery box' method of nihilistically exploiting the audience, and turn it off quickly if it seems like that shit in game form. Ignoring Codex-beloved classics, we are talking about the other 98% of the genre here.
It's these generic 'Neverwinter Nights' tier games that modern RPGs are emulating too. Rather than trying to be exceptional experiences like 'Vampire: The Masquerade - Redemption' or 'Planescape: Torment', that actually add some energy into the system. Things like 'Solasta: Crown of the Magister' or 'Pillars of Eternity' are, for all their pretty production values, unexceptional.
Resident Evil 1, Dino Crisis 1, Tomb Raider 1, Star Wars: Dark Forces 1, Star Trek: Judgement Rites, Metroid Prime 1, Super Metroid, AvP 1, Doom 1, Thief 1, etc, don't suffer from this. Those games say what they mean, concisely, then leave while you still want more. They feel visceral and immediate. It's an RPG specific thing. Incidentally, you can believe you are killing hundreds in Doom; it's you aiming, after all; with some luck, one guy could massacre a horde one-by-one, with a gun. In an RPG, the logistics of what you are doing sometimes become absurd.