The cloud is truly someone else's computer, and it's not limitless. From the perspective of the individual, it might seem like you could scale infinitely if you need more boxes, storage, or networking, but ultimately the cloud vendor (Azure, AWS, GCP, etc.) needs to have spare machines around. Many of them do, and that works well at the scales in which they operate.
To a point.
Azure is having capacity issues in some of its data centers. I'm sure that all of the major cloud providers buy lots of hardware constantly, but there have been shortages during the last year, which has meant for Azure that DCs are running out of capacity. At least for the rest of 2022, which is likely driven by both a limited supply of new machines and the growth of cloud usage by their customers. I know I've seen continued growth in companies moving to the cloud for various services, including their data services.
I haven't seen reports of large AWS issues, though they do have plenty of instances of insufficient capacity errors and solutions. GCP has similar reports.
Truly, the cloud is the cloud vendor's computer. It's also the cloud vendor's infrastructure with lots of tooling to help you manage software configured networking and storage in addition to compute engines. It is limited in capacity, especially when lots of customers want to use these resources in one particular data center. That capacity is usually quite high, but there is definitely a limit.
Does this mean that the cloud isn't better than your data center? That's an "it depends" questions. The cloud is great in many ways, and far superior to a lot of private data centers (or colocations facilities) that I've worked in or seen. I think the cloud is fantastic, but it's not perfect. There are limits and issues at times, and you should be ready to work within or around those limits.