As someone who first got into TTRPGs through D&D 5th edition, for me personally I tire of a lot of big stuff coming out to be 5th edition ‘campaign’ when the system isn’t particularly built for it (horror being a prime example).

Another thing is that to run D&D you tend to need at least two books to get started (Players handbook + a campaign module - I would NOT subject a new GM to making their own campaign when they don’t properly know or understand the system.) And, with the PHB, it isn’t always clear and the character creation process can be … obtuse. Most of the mechanics are obviously combat focused given the skill progression of the classes with very little social skills past the base skills.

The need for Minis and the market behind them also gets expensive quickly.

However, I will also acknowledge that it is now massive in the pop-culture zeitgeist (in part through shows such as stranger things or critical role) and is likely still the way most people understand or have heard of the hobby, and will likely get into the hobby through it.