In Denmark, turnout is consistently 80+%, and we don't have online voting. Clearly, it's not the lack of online voting that's the (sole) problem.
I can see how it's practical, and probably inevitable in the future, but quite frankly, if you can't be bothered to spend an hour every two-three years voting, I really don't need your input on who should be in charge.
Voting should be harder, if anything. Then politicians would have a higher lowest common denominator to speak to.