S3 has many open implementations you can self host. Some are quite lean even. Unless you need really complex IAM stuff it's a solid and rather simple experience to run it.

Perfect is the enemy of the good. While there's an ideal case where you're hosting it on a box in your house, that's not for everybody. So while hosting it on AWS doesn't remove every dependency on big tech, at least it's not a full on Google hosted SaaS product.