This is obviously a marketing article. Docker containers take up essentially zero resources. Try running the hello world image and tell me how much ram and cpu and drive space it uses. As Lukas mentioned earlier, it depends on what you run. For example, do you really need 10 full instances of Postgres running for devops purposes? No!

The main reason i use docker is to spin up something temporary or for multi-tenant purposes where you want security separations. But ProxMox is way better for that. So really all I use it for is temporary stuff.