Many of the skins are developed by MC users, including the default Modern Cards dark version you are using. Why a "skin creator" does anything a particular way is typically a design choice, but can also be attributed to the way they specifically use MC. For example, if the skin designer only clicks in the middle of the close button, it never manifests in their testing that when the cursor is pushed into the extreme top-right corner of the monitor the close button does not activate (due to the button "offset" they specified). I am not saying that is what happened here, just speculating on a possible reason.
In any event, you can easily "fix" this - just edit the skin's main.xml file and change the button offsets yourself. In the original XML, the close button is offset 1 pixel to the left , i.e., OffsetX=-1 (but OffsetY=0 for the close button which is why it activates along the top edge, but not the right edge). The min/max/restore buttons however, are all offset 1 pixel down (OffsetY=-1), which means that running your mouse all along the monitor top edge will not activate those buttons. Instead of walking you thru the necessary edits, I just did it for you and attached the modified main.xml. I only changed the input parameters for Windows OS (Win10/11) - I did not edit the Win8, Linux, or Mac parameters for these buttons.
NOTE: The Modern Cards skins all have OS specific parameters for all the window sizing/control buttons (most skins do not), so you only need to adjust the parameters for the OS you are currently using. You can change the offsets for all the other OS parameters if you wish, but they will have no impact on the "active" OS. If you want this button activation to work the same on another machine with a different OS, you will need to edit the corresponding OS parameters for each button.
You first need to copy the entire Modern Cards Dark Skin folder and name it to whatever you want - I recommend Modern Cards Dark (modified). Then copy the attached main.xml and overwrite the existing main.xml file in the NEW folder. Creating a new/modified skin folder is necessary to preserve these changes, as MC overwrites the default skins/folders every time you install an MC update. After you complete all the above, the skin menu will show choices for Modern Cards Dark Version and Modern Cards Dark (modified). FYI... that will be the name of the skin in the menu regardless of what you name the new folder - the skin name you see in the menu is driven by the first line in the XML file, NOT the folder name (change the folder name to whatever you want to verify this). If you want to change the name you see in skin menu list while using MC, you will have to modify the XML yourself to change that.
FYI... the forum does not allow uploading an .XML file, so I changed its extension to TXT. You can download the file and edit file properties to change the extension back to XML. Or you can open the new main.xml in the new folder, and then copy/paste the entire text file contents over the XML contents. Either way will work.
And finally, be sure to reload the skin after making any changes. You do not have to restart MC... just go to the skin menu and choose the same skin again for the changes to take affect.