I will refer to the most important comments:
1. The new UI is indeed an attempt to sale, in a sense that to attract a group of users for which the current UI is not attractive. The size of this group is difficult to asses, but my guess (wild guess) is that as much as 50% of possible users could be lost. This does not mean of course that the current UI will be dropped.
2. I maintain that the current menu is clumsy and that can be measured. The changes to make it straightforward go beyond just the menu itself, so this is just the first and most important change. For example something that cryptic like "Delivery against sales order" should be turned into an "outstanding" "filter" in the "sales order view". In the same manner creating an invoice should be a "create" button in the invoice view, as it is now with customers (almost). It that sense "functionalities are grouped together". Anyway I understand your point, that is the point also why we use the linux console, which is a 1-level menu, but the majority of users do not use an OS like this. Again, this does not mean that the old menu should be dropped.
3. In Odoo you need more than 4 clicks to create an invoice, providing that the client is already there. I do not say it is a right solution, but my aim is to attract the most users possible, and your standpoint (@elax) represents expert users, so those needs exclude themselves. So it is perfectly understandable that you are unhappy with the changes.
4. The menu in its design is thought to be a 2-level, with the 3rd level being supportive only. The idea is that most important functionalities should be accessed by 2 clicks, but there is some work still to be done. This for example could be achieved by accessing the "direct invoice" directly when a user clicks "invoices", and add "transactions" as a separate entry in the "sales" menu. Anyway as proposed in point 2, I would prefer to focus on adding shortcuts than designing a "perfect" menu structure.
5. The point against adding a customer (by @elax) is a valid one but a proposed solution is a wrong. The proper solution is to add a popup menu with the possibility to add a customer in the "direct invoice" screen. By the way I wonder it has not been done yet, as it is an easy change. Following that way of thinking the screen "customers" would be for searching and only secondary for adding.
6. The "sales config" has been moved to the setup on purpose. The changes there are being made once in a blue moon so it is right to move that functionality deeper. What we care about are the most popular screens, the less popular are of course not so important.
7. The ubermenu is a cool idea although not a new one. I agree this could be a way to go, but for the moment what we have is enough, so it is unlikely I will put more effort into it.