Multitenant architectures are valuable in that you can reuse a lot of the same resources e.g shared infrastructure but they also come with caveats. Much more complex to create, harder to manage and reason about. When things go wrong they affect a bigger subset of users. There's potential to mess something up and expose one tenants data to another. I mean just hosts of problems. When it works it works well but not without a lot of overhead. Having built and run it from scratch and the alternative of serving isolated deployments per customer I can't say one is better than the other. It's that they're used for varying scale just like different algorithms or monolithic vs microservices. It's not one size fits all. You have to understand what you're getting yourself into. Saying that I think more software will start to bake in the concept of multitenancy so we might just start getting it for free.
Indeed, most of the cloud providers such as AWS, Azure, GCP use the concept of multi-tenant architecture. It hides lots of details from the end user and efficiently utilises computing resources.