No more toolbar, no more save, no need to be initiated to planning methodology, this solution has everything to please. But, even if you have modest needs and you are not an experienced project manager, you quickly reach the limits of what you can do with Project for the Web. The functionalities are limited, and one would like to be able to do more, that is the paradox.
Having said that, Project for the Web is a solution in perpetual evolution, to which Microsoft adds new functionalities at a very fast pace in 2021 (see this link for planned updates https://www.microsoft.com/en-us/microsoft-365/roadmap?filters=&searchterms=project).
But Microsoft can only deliver generic functionalities, useful to the greatest number of people, but cannot foresee the specific needs of each one. There is no doubt that the most requested needs will eventually be made available by Microsoft, but they will be provided in a generic form that everyone would like to adapt to their needs.
The need to consolidate projects into programs or portfolios to provide management with a global view of the activity, advanced characterization of projects to add personalized data (the name of a sponsor, a budget) that can be consolidated between projects, data linked to projects (lists of risks or problems, key milestones) are all customizations that will make it possible to make projects consistent and aggregate information.