I use Medium sporadically, and I think it's a good platform to use if you don't already have an audience, since it's easy to repost to larger publications and gain distribution.
Once you gain an audience, or if you already have one, then using an open source platform is the way to go.
WordPress is probably the best choice, since the ecosystem is just so much larger than anything else out there. I would really suggest finding a managed service over deploying it on an ec2 instance or something. Security is a constant battle on WordPress sites, and it's just better to have someone else deal with that.
If you don't care about distribution or growing an audience and are just blogging for fun, then something like Hugo might be a good choice.
