It depends on the science. There are plenty of amateur astronomers, geologists, anthropologists, and even some types of biologists and physicists.
It also depends on what you want as an outcome. If you want to discover things, then you can do science. However, if you want to publish in order to counter prevailing theories, your road is going to be much tougher without some establishment credentials.
If you think serious == published, there are ways to get back in the formal game without a degree but with technical expertise. For instance, across the science landscape, technical specialists are valued as research assistants and there are jobs or internships to be had. It just depends on finding a good match of your skills and interests with a lab that fits and has specific needs.
My advice is to follow your interests, find researchers working in that terrain, then contact those that are physically and intellectually closest to you. Think about what you can offer, even if it's as simple as helping to automate their processes. It might take a while to find a good match, but there's a place for you.
