In some cases, the services (and government as a whole, and big companies) don't take advantage of pre-existing skills or aptitudes. In other cases, they do -- there are incentive/recruiting/fast-track systems for certain types of professionals. They've gotten better about this since becoming an all-volunteer force vs. draft. The big problem is that there is a "military way" to do a lot of things, largely focused on big-vendor enterprise in the IT space, and you have to work within that. Getting affiliated with a lab, DARPA, etc. is probably the way to use more interesting tech.
One problem I have personally is that they're very credential-focused; as a high school and college dropout, I'd be kind of screwed. Otherwise I'd be really interested in reserve/NG in certain specialties (psyops, civil affairs, infrastructure parts of embedded advisor teams, rotary/uav aviation, sigint, SAR, medical, diving). It would also be really difficult for a startup founder vs. an employee at a larger tech company.
For the donation/volunteer argument, rather than just donating money, my plan is to do NGO work on the side, and hopefully eventually be able to set up a specialty communications-in-conflict/disaster zones infrastructure NGO. A lot of charities ARE saddled by large numbers of unskilled volunteers (or at least without specific relevant skills), and structure their operations to be labor vs. skill intensive.