I was 24 when the 3E Player's Handbook was published, so just at the upper end of their target audience (but I had stopped playing 6 years earlier). This art style did appeal to me at the time for whatever reason (although I dislike the 3E elf look, I much prefer the 3E halfling look to the way 5E art depicts them).
The Dos and Don'ts are quite interesting in terms of what had probably changed and what hasn't in the ensuing 21 years.
"The monsters aren't misunderstood - they're EVIL!" is funny. As a kid, I HATED when the monsters were just misunderstood. I think it's fine now. In 5E, the monsters are usually evil, but sometimes they are indeed just misunderstood.
"Accentuate the history of the game and always talk about how millions of people play" is obviously still a big part of their marketing.
"Don't show nerds, geeks, and children" playing is also funny. Are there still nerds and geeks today? Or rather, isn't everyone a geek now? I guess this was still a huge stigma in 2000. WotC obviously is very keen on showing cool, attractive people playing D&D as much as they can - but they still let the occasional obvious nerd or geek be seen as well. Kids playing aren't completely censored in 5E marketing but are definitely portrayed as more of a novelty or a side bet - and you almost never see kids in their marketing images, they just show the PRODUCTS aimed at kids.
"Don't suggest the game is about dressing up in costume" - not that 5E suggests D&D is about this, but they're obviously much more comfortable with this now due to the rise of cosplay. The anxiety about it here reflects post-Satanic panic concerns. Same deal with "Don't use pentagrams and devil stuff"; they're pretty much fine with that now.
Like 1E, 5E is clearly more comfortable with the occasional anachronism than 3E was.
"Don't present impossible moral dilemmas" I think is probably still in place for official material - I'm trying to think of an official adventure that deliberately presents one and I can't. Icewind Dale: Rime of the Frostmaiden suggests one with regard to the Ten Town sacrifices but chickens out when it comes to really putting it in front of the players.
Interestingly, the Dungeon Master's Guild terms & conditions have no such injunction on moral dilemmas so you do see them in DMsGuild adventures.
Don't show drug use or drunkenness is clearly out; you do see both in 5E (although never real-world drugs).
"Don't show the heroes dying" has clearly stayed. 1E certainly did do this (the example of play provided in the 1E Dungeon Master's Guide includes the death of a PC, and Larry Elmore's rather famous painting of Sturm Brightblade's corpse with a hole punched through his breastplate comes to mind). I think every edition since 1E has eschewed it.