This is exactly the situation I´m currently in. Company decided to migrate from big on-prem kubernetes to AWS. Now every team got their own account and well... good luck, you´re on your own now. We´re a small team of three developers. Although we have three certifications under our belts (AWS Dev, CKA, CKAD) it took us almost three months to configure AWS and set up the Terraform pipeline and define processes like "upgrading cluster". The "enabling" part was basically missing in the whole cloud strategy of the company. It was more like: good luck, you´re on your own now.
In fact we made contact with a neighboring team. Only to find out that their use case was so different from ours that collaboration didn´t make any sense. For them Kubernetes was not a good fit, for us it was the way to go.
Speaking of sharing a cluster or AWS ressources: we figured out that it is not allowed due to billing reasons. Company policy is: One product per AWS account.
If you ask me I see a shift of paradigms happening here. Now you hear a lot about "enabling teams" instead a dedicated team for infrastructure providing services (e.g. the Kubernetes podcast from Google). I´m not convinced yet. I think this is more like kicking down responsibility down the chain. And then it feels more like: Someone needs to do the dirty work but nobody wants to do it.
It might work if you don´t have to provide Service-level agreements (in our case: we don´t). For us it is just more work to do. And our work shifts from dev to ops. Instead of writing software we´re mostly busy with configuring cloud resources. This will ease a bit once everything is running. However: I see this whole change more as ... uh, strong word... ideologically motivated. Cui bono? Neither our team, nor our users nor our infrastructure bill.