I was somewhat surprised that IRIS Analytics was not required at all since there
was no Cube nor Pivot nor Dashboard. I built it myself just using dc.dc.bi.PopSongs.

Yes, IRIS contains IRIS BI for analytics but it needs additional skills to know it. 

We want IRIS users to be able to create analytics solutions if they know PowerBI, Tableau, and Logi and use it vs the data in InterSystems IRIS

I understand them - they indeed provide the cloud infrastructure to host the development and to build and deploy containers then. Somebody pays for all this pleasure.

Nobody prevents from setting up the personal infrastructure similar to CodeSpaces even now. I don't see very much need for myself yet - my mac laptop is enough productive with VSCode and Docker desktop installed.