I think cloud computing is an implementation detail that nobody outside of tech really cares about. People who sell IT services try to spin it as this big thing, but for people outside the industry it's just not such a big thing. Yes, it's easier to rent servers on demand now, but does that really make such a big difference?

To me it's similar to how engines with direct fuel injection are so much more efficient, easier to handle, more reliable than engines with a carburetor. They were so much better that no current car uses a carburetor any more. But nobody would say that better gasoline engines were the big new thing that happened in the 90ies.

Is cloud computing not just a rebranding of mainframes?

Although cloud gaming could be the next big thing. Now people can play even if they cannot afford a gaming pc (I for one have not had a dedicated gpu for like 15 years)

Cloud computing is not yet a huge thing. Only 5% or so of corporate IT spending is for the cloud. Economically cloud computing is significantly more expensive so it only makes sense in a limited number of use cases (for example startups or when you have a massive temporary increase in demand).