You don't understand genericization. Kleenex and band-aid, as an example, are still easily enforced trademarks despite being the go to examples. Neither has been genericided, and it won't happen to D&D either. Not only that, but the actual difference between a band-aid brand bandage and any other "band-aid" is miniscule compared to the difference between D&D5e and most other systems, even those trying to invoke it like DC20.