Egor, I get you and fair points.

I just thought that having a modal to do all the transformations similarly to Photoshop's free transform would be cool and it doesn't have to interfere with other tools, that would be still useful for the precise input of numbers for instance. All the elements seem to be there, but not working unless you switch to one particular tool first.

I use separate tools for moving, rotating and scaling in 3D softwares and they make so much sense there (but even then, most 3D apps updated their gizmos to have all the transformations in a single universal one). It makes sense in a 3D software because the intent can't be clear with a free camera and so on, but on a flat representation like in Illustrator, they make more sense to be together: The intent is always clear. Photoshop is proof that it's possible and very convenient.

Take MoI 3D software for instance. It doesn't display the bounding box in free camera mode and you have to choose the transformation tool to use, but once you snap to any flat view, it shows the bounding box around the selected items and allows you to move, rotate and scale them without changing the tool. and it's a 3D software made by one man, mind you. Not a flat vector drawing software that is several decades old and industry standard. It is not made by the company that created the very convenient free transforms in Photoshop, only to have a more clunky ways to do it in Illustrator. MoI 3D of course lacks lots of necessary features for vector-drawing, but it handles many things a lot better than Illustrator, this is just one example. Another would be that you can access points on edges, even of 3D objects, without having to switch the selection tool.

Adobe proved that it can find solutions to improve upond or even completely change features without breaking anyone's workflow. Sometimes, all what it takes is a checkbox in the Preferences menu to revert to legacy or to use a certain feature.
Anyways, my rant is over. I strongly believe there's progress to be made in this area that would make the software more accessible and robust. I believe that optimizations in simple repetitive tasks are more important.

We need 5 different tools for basic operations for several reasons.
1. Legacy. If it works — do not change it. You can call it 'consistency' too, but with previous versions. You say it matters to you!
2. Simplicity. Having one tool that have only one dialog that is easy to navigate and enter values, using a keyboard, is much faster than tabbing through a dozen of fields (or even locate if you are using mouse/pen), which Transform Effect dialog has.
3. Learning and diversity aspects. Some users prefer using tools to learn the basic transformations, and some users prefer using separate operations instead of using bounding box’s markers. You are not forced to use these tools at all, you can remove them from the toolbox if you want (you don’t use Flare tool probably? some do)

I understand you frustration though.
Changes are important. But you should always remember this situation — https://xkcd.com/1172/ :)
I like the idea of having a Transform-Each-like dialog that applies a range of transformation to a selection (rather than all items in selection, like Transform Each does). And I vote for idea of having sticky pivot controls. These are all valid points.

Maybe. To me, consistency matters, and not having to switch between tools in order to just do simple operations is a plus. I like the Transform effect menu with all the transformations in a single place. Why do we need 5 tools for "destructively" doing transformations, each with its own menu, and then there's another non-destructive effect that does it all in a menu that looks nothing like these separate tool menus? All These menus and buttons can be consistent, which helps with muscle memory and take less brain power IMO. This fragmentation throws me off. It's kinda tolerable to have it in different Adobe softwares, since probably not the same teams work on them, but I find it strange to have it inside the same software. It would be great to be able to pick up any software and have a streamlined experience. It is very possible, and it seems that Adobe started with this in mind, but then everything branched off for no reason.
I don't buy the muscle-memory argument. I know that millions are used the clunky ways, but this is no reason not to improve the software. To me, it seems more like a Stockholm syndrom to accept it the way it is and resist change.

Hitting Enter should give a dialog or an options in the current paradigm. Free Transform has none, and it could have a merged version that allows to set a relative position of the pivot and allow to tweak transformation values... scale, rotate... also shear, distort, perspective! So instead of simplifying we get a more complex dialog instead. I'd still prefer one, but also keep separate tools: Scale, Rotate, Shear. Having simple dialogs is better than having only one complex, because the speed and muscle memory matter.

The move, rotate, scale and free transform tool can be merged into a single tool, and pressing Enter would give universal control just like in the Transform effect. Maybe pressing a modifier while hitting Enter to access the parameters of just one transformation. Illustrator is full of features that can be merged and simplified to make the experience a lot more seamless and the software a lot easier to use and learn.

Nidhal, while you can’t change the position of the pivot, using a Selection tool, with the Bounding Box controls, you can reposition one using Free Transform tool (E key by default)...

Still it's quite rudimentary! It does not snap to anything (with Smart Guides or Grid, whatever), it can’t be fixed (obviously).

So I vote for making it better.