Imagine you want to deploy some microservices to Kubernetes. You can just create EKS/AKS/GKE cluster from the GUI, `kubectl apply` a few resources and create a load balancer to point your domain there. That will work. But...
You probably want to automate the infra creation (so Terraform, Pulumi, CDK...), you want to automate building (so GitHub Actions, Jenkins, Bitbucket Pipelines, GitLab CI...) and artifact storage (so Nexus, Arti, ECR, GHCR...), you want to automate deployment (so Argo, Flux, Helm, Kustomize...), you want to automate monitoring (so Prom stack, Datadog, many APMs, Splunk, Graylog, ELK... could easily name a dozen more).
Each part of the stack can easily bring a dozen different tools. I work in SRE and I use at least 40-50 tools for a mid-sized project. And this is "normal" :)
Meh. For a long time people have been saying stuff like "devops is dead, long live the platform engineer" exactly because the figuring-out-what-works phase of wild experimentation is over and there are unambiguous "winners" for technology in most every niche. You've listed lots of commercial vendors and alternate choices for backends/front-ends here as if to illustrate a lack of standardization in tools/frameworks, but is it really?
Whereas churn in web-dev seems self-inflected.. devops practitioners don't actually create vendor/platform fragmentation, they just deal with it after someone else wants the new trendy thing. Devops is remarkably standardized anyway even in the face of that, as evidenced by the fact that there's going to be a terraform'y way to work with almost all of the vendors/platforms you mentioned. And mentioning 20 ways to use kubernetes glosses over the fact that.. it's all just kubernetes! Another amazing example of standardization and a clear "winner" for tech stack in niche.
Well, many years ago you could use CFEngine, Puppet, or Chef, or Ansible, or Salt/SaltStack, and then later Terraform, Otter, Pulumi, and now we have Nix, and a Terraform fork as OpenTofu.
Not all of those tools do identical jobs but there's a ton of overlap within them and they all have idiosyncracies.
