Grogs haven't actually had much impact on 5E's success. I forget the percentage, but the percentage of players over 35 is pretty surprisingly small compared to the rest.
In fact, I'd say it's wrong to say that "being in touch with it's roots" made 5E particularly successful, given the age of people playing. I think 5E's success comes from it being an accessible and pretty playable game, combined with streaming/YouTube and particularly Critical Role introducing it to a mass audience at exactly the same time a ton of '80s nostalgia was around (none of which requires 5E to be in any way like '80s D&D, indeed, it basically isn't), and also hitting at a time when a lot of 20-somethings were looking for stuff that was social but fun and yet also not necessarily super-drunken (board games got a huge boost from this at the same time - indeed at board game cafes in London, the "grog" percentage, i.e. people my age and above, was like 10-15% tops - most people were clearly in their 20s and highly diverse in terms of both gender and race (which was delightful to witness - seeing two Middle-Eastern girls in their 20s playing some serious LCG deckbuilder for example!). Accessibility and hitting at the right time are key to 5E.
As for racism, I do think there is a bit more in older D&D fans than I'd like, though, honestly, I'm skeptical about how it compare to the general population. Older RPG fans skew white and male, but they also skew liberal/leftist/open-minded - D&D fans less so because you get more people who like the black-and-white worldviews they see alignment as endorsing, and like to romanticize the past more - but still I suspect compared to the population in general it's not bad.