It helped me a lot to focus on things that I like: development instead of ops. I never had to SSH into any machine or do things manually. I just tag a github release and in few minutes I get my application updated.
With Docker I believe it would be lot more complicated, no zero-downtime upgrades, no load balancing, OS vulnerabilities. Then, when I would need to add a new service into my setup, I would have to yet again go into the host or multiple hosts :)
So no, I don't believe people who say that for small projects you shouldn't use K8s. It saves a lot of time and helps you not to burn out on your side projects as it takes the pain of running a service away.
P.S. I am an author of Keel https://github.com/keel-hq/keel, it's a relatively successful CD solution, I hope it saved a lot of hours for other companies too :)