I would support compulsory voting, however it would need to be very, very safeguarded against Jim Crow laws. Simply put, compulsory voting needs to be rooted in uplifting communities and from a place of education.
I would say something like a one week voting period during which time American's learn about their local candidates, policies, and anything else about the platform. It should be treated like career day, where the entirety of the time is spent learning about things that we don't see in our day to day lives.
However, even that I know would fail. Just looking at Trump rallies should be enough to prove that it is still flawed, because inherently it being a group of people with an ideology of hatred will come up with the worst possible {gestures at something all encompassing} imaginable.
That said, I do think having some ~40% of American's actually voting is far, far too low. Increasing this through citizen engagement is probably how it would be best accomplished, but again, you have 63% of American's voting for Christian policies, not for American policies. So ultimately, we are in a stage where Democracy is mathematically at odds with the base of voters, with two parties that only represent a small portion of their constituents (R's with persecution through religious corporatocracy and D's with corporatocracy) all while the rest of us are just trying to vote to get some local changes that will have a positive effect.
All in all, while I support a form of 100% voting, I do think it's a multifaceted problem ranging from the issues others have mentioned, to including everyone in the vote means we also get the entirety of places like Utah and Idaho who do not want people like you or I to even exist. Not to say I want to exclude them, but I do not want policies based on anti-humanitarian agendas or hatred -- that is incompatible with and antithetical to the progress and betterment of humanity.
In our current state, any form of compulsory voting will be primarily anti-humanitarian because that's what religious voting necessitates. For compulsory voting to be viable, we would need to bolster education for both emotional and critical intelligence, and I would consider a more than single day period of voting.