This is an interesting point! I have definitely noticed that something in the quality of TV now really makes me much more content to just sit back and let the story happen and only really engage on a, like, reblogging-gifsets level rather than as a more active participant. I think you make a great point that all those iconic fandoms of yesteryear really had a messy element that made it feel easy to jump in somehow.

Now I am pondering what, exactly, it is that motivates me to actually write fic for something as opposed to just being content with canon and not feeling motivated to jump into some version of that world myself, so thank you for giving me something to ruminate on, hee! I think it is usually either that canon is missing something that seems really full of potential to me and I just have to wander down the path of How It Would Go (typically, people who should be in love, obviously, but also maddening canon writing decisions that seem to lack logic or emotional truth), but also occasionally it's just that the ship is so wonderful that even though everything in canon is satisfying, I just want to spend more time with them. (The first ones that came to mind for me re: that vibe that are currently pretty popular are Eve/Villanelle and Crowley/Aziraphale, which are somehow the most different two ships you could ever imagine, but also weirdly same in my psyche??)