k8s isn't only for microservices. You can containerize up normal applications (12 factor or otherwise architected) and run them on k8s.
Is it a good idea? Depends.
On the plus side: You have one underlying runtime and orchestration layer, with a lot of useful primitives (including and especially around deployments).
On the negative: You introduce yet another layer of complexity and abstraction.
You just described the counter to “don’t run things designed for Google if you’re not Google.”
The real advice is “don’t run stacks that make trade-offs or give up guarantees to be able to scale to a size you’re not at or solve problems you don’t have.”
The systems in kubernetes for horizontal auto scaling are extremely nice and work very well for our large monolith. At this point I can't imagine deploying any system with significant batch or online workloads any other way.
We switched to k8s early on in the company and that little bit of work to get it operating with HPAs, etc has paid off in dividends over time.
Is it a good idea? Depends.
On the plus side: You have one underlying runtime and orchestration layer, with a lot of useful primitives (including and especially around deployments).
On the negative: You introduce yet another layer of complexity and abstraction.