You vastly overestimate the difficulty. The reason we're commonly told not to roll our own crypto is because it's easy, and also easy to get wrong and possibly catastrophic if you do. But many perfectly serviceable algorithms are simple and public knowledge. Arguably a scenario where everyone's using their own crypto and half of it's broken is still better than everyone using the "industry standard, pre-backdoored for your convenience" version.

Of course it's utterly trivial to make a one-time-pad cryptosystem, and more practical in 2017 than ever. So what if the keylength must match the message length, my phone has a 32gb uSD. That's a lot of text messages.