Indeed you can. It's much harder though. If you have a full-time job unrelated to your research, you need to self-fund a lot of expenses. You need to convince your boss to let you take time off to go to that conference to present your work. You need to foster connections to other researchers through activities like reviewing for journals, etc.

Of course, you can bypass all that and just publish straight to the internet. Personally, I find that to be enormously difficult. The interactions with my peers -- the conversations over beers in the evenings during conferences -- are so useful. Losing those hurts your ability to do good work.

I get that we're all humans and feel better if we converse face to face sometimes. I certainly appreciate people doing research on their own expense and time for the general good.