In this response, I will only consider the ability to detect the characteristics and I will not discuss mere graphic design or aspects such as the size occupied (since they are very specific to the implementation).
In my opinion, there are two aspects in the ability to detect features:
The first is Discovery by the user without any external information: Simply by visually scanning a tape, one may or may not be able to recognize a particular feature. Without knowing on which tape a certain characteristic is placed, one has to change through each tab, just like what could be done with the menus.
A small disadvantage of the tapes in this regard could be that the buttons are "everywhere"; they come in different sizes and their design is (although rectangular), consequently "chaotic" (for example, take a look at the Slideshow group in this screenshot). This contrasts with the menus, which have two clear columns (one for the icons and one for the title of the command).
In addition, some of the icons in Ribbons lack the text, which is not useful if you are looking for a command and have a certain idea of what it is called, but you have no idea what your icon would look like. In this way, commands can be hidden "with the naked eye" on tapes, which is never the case in menus.
The second aspect is User-based discovery based on instructions: In my opinion, this is where the tapes are incredibly weak compared to traditional menus.
The first problem in this regard is related to tapes that do not show any text for some of the commands. For a menu structure, textual instructions (in a tutorial website, in a book, in a chat window or spoken by phone …) can easily convey where to find a particular command in a menu (example found in many applications with this wording, although not necessarily MS Office): "Click Edit -> to import -> From the archive -> Via plugin. The same is rarely possible for tapes, as some icons do not show any text and texts are displayed in different locations. For an example, see the screenshot mentioned once again: some texts are to the right of the icons, some below, group headers are below, tape headers above.
Essentially, it is the same reason why, with traditional menus, such instructions generally refer to the menu instead of the toolbar.
In addition, in the menus, moving to the next hierarchy level is a simple activity that works in the same way at each hierarchy level: place the cursor over / click on a menu item and a nested submenu appears. In Ribbons, on the other hand, each level of hierarchy works differently. Sometimes it is a tab, sometimes a group (in the case of groups, no input is required, just visual scanning), sometimes you must click on a group's header to open the "group dialog box "(and even that is not uniform, since some groups do not have a dialog box and their headings cannot be clicked), sometimes, you must open a drop-down menu from a button, which makes the whole process very confusing.
P.S .: Many answers seem to confuse what is and what is not part of the "ribbon interface" as such. One of the most controversial properties that is often cited in the answers here and elsewhere seems to be the reorganization of a variety of options. Those who praise Ribbons sometimes praise them because they perceive that the grouping in Ribbons is more logical, while those who don't like Ribbons (and also those who talk about users who don't like Ribbons) often point out that users accustomed to the old menu structure are used to the above. command grouping and, therefore, gets upset because they have to relearn where to find the commands.
Nevertheless, that change simply coincided with the introduction of Ribbons in MS Office, it is not inherent to the ribbon interface. The same reorganization could have been carried out in the old menu structure.
The same applies to a reallocation of keyboard shortcuts. Some keyboard shortcuts for certain commands were changed at the same time as the tapes were introduced, but they could also have been changed at any other time. Again, different shortcuts are not an inherent feature of the user interface of the ribbon.
Thus, the commands are grouped in a more logical way Y users are reluctant to change and have to relearn they may be true and valid points, but they are not related to the user interface of the ribbon.