For me, the internet officially died when various game developer forums shut down in favor of just using places like Discord or Twitter. Specifically, it was when the Elder Scrolls forums switched to their fucking god awful Bethesda Forums approach and then a few years later were mercifully killed.
Nothing will ever replace the TES forums for me. The level of in-depth autistic discussion about mods, gameplay, lore, and then general discussion was too awesome throughout the 2000s and early 2010s.
At least the UESP forums still exist and are relatively active.