Most probably, no. This opinion is based on two considerations.
1)Being unable to join the academic stream means that other work decisions have been taken. Inevitably this leads to inability to focus 16/24 on a physics problem ( I put some time in for sleep). People who have left their mark in the history of physics were very focused on it, and focusing I would consider a prime prerequisite.
My no is not a complete one because in this day and age we have the internet. If the reason one is unable to join academia is something like Hawking would have suffered if his disease caught up early with him, or if one is taking care of a very sick loved one, there is still the internet to learn the latest and discuss the most important, currently. As long as time is not a problme . Which brings me to the second consideration:
2) I had a professor in ancient greek who imparted the following wisdom: Knowledge is a circle. There is a frontier where explorations go on, but the more you know, the larger the radius, the greater the frontier. Unfortunately now there is an enormous body of knowledge continuously expanding and continuously needing new tools. Within academia a sifting takes place through discussions, coffee in the cafeteria, informal lectures, conferences, long before papers for peer review are ready. Ideas are threshed out and collaborations set up that allow for faster knowledge accumulation. Some of this may start to happen on the internet and it would need a particular type of personality to be able to survive without the face to face interactions.
Now if he/she has the focus and the time to pursue a physics problem that is not contradictory to known experimental facts and proposes new experiments ( i.e. it is falsifiable) then I wish them luck. I think the peer review process in physics is not too biased to look at a paper on its merits, but in any case there exist the archive locations where a paper can be put up on the internet and discussed on sites like this .