Blender is 28 years old.
During a large portion of its history, shortcuts and UI were not customizable. There was a mode dedicated to UVs before that a Face Select Mode exists, in Edit mode. And there was no ability to sculpt anything.
Modes are a legacy of such period.
Modes are a way to limit display of tools.
Such categorization of tools may seem arbitrary to any user, according to workflow user developed.
But in whatever 3D software is used, UI does not display permanently the whole potential of software.
You just showed an UI exposing 33 tools, accessible from one button click.
In current blender’s sculpt mode, there are 47 buttons in toolbar.
Other software have tools that would correspond to set of equivalent blender tools.
To be really fair, you should consider them as mini-modes or sub-modes or brushes that can be derived in different presets. There is no way to have direct access to everything, whatever the software is used.
If you want to have a glimpse of what suppression of modes with only basic tools can look like, take a look to Grease Pencil in blender 2.79 before it became an object with modes.
UI was cluttered. Shortcuts were cumbersome.
Blender devs can not provide a unified mode without rewriting tools to fuse many of them into one, what would displease probably more blender users that the ones annoyed by modes.
Better solution should be ability to allow creation of custom modes.
But that still needs a lot of work to be sure that tools have been created to be used in different modes will be compatible in a unified mode.
There is a little bit of that, in Julian’s design. He is thinking about the way to present mask tools in new paint mode, how to store them, how to also add face sets, etc…
It is not fair to complain about too many modes in Blender, when developers started the work to suppress one, and renounced to create a requested Retopology mode.