I think that the presence of writers at cons has gone down significantly actually.
There was a time when every dedicated Trek con I attended would have a panel with a writer. I remember first seeing Peter David that way. It’s what first got me trying the books.
When I look at Mack or Ward’s social media, they’re only doing 2 or 3 regional general science fiction cons per year.
As the paid availability of actors for photos and autographs has increased, we see more of them at cons, with big panels instead of single presenters. It’s however the presentations by writers and production folks that I miss. While one here’s about as much from them through podcasts and featurettes, it’s not the same as in-person.