At least in our org security let us know when it's time to patch various components and it's typically just a devops chore to bump a helm chart version and merge..
I don't really understand your point; You're trying to say managing a single helm release for istio is more effort than (in my case, for example) manually managing around 40 TLS certificates (and yes, we have an in-house PKI with our own CA that issues via ACME/certbot etc also) and the services that use them? It's clearly not?
Just templating out the config files for e.g Cassandra or ES, or Redis or whatever component takes multiple x the effort of ./helm install istio.
Istio is a notorious pain to maintain, because it has a bunch of dependencies around Kube clusters, so you can't just helm install istio every time there's a new release.
Every component needs a different tls configuration, vs one time installing istio.
Raw TCP is supported by istio even with mtls, you just have to match in your VirtualServices on SNI instead of Host header.
We routinely mix tcp and http services on the same external ports, with mtls for both.
UDP I don’t really see how is relevant to a conversation on tls