There already are shortcuts for closing other tabs.
If you have a mouse, you can middle click to close the tab you are currently hovering over.
If you are using a trackpad, you can configure shortcuts like that and much more with BetterTouchTool (https://folivora.ai) or other similar programs.
Moreover, if you hover over a tab, an X appears, allowing you to close said tab: 
If none of those fit your workflow, could you list browsers that currently have ⌘+click shortcut for closing tabs, if there are any. Additionally, how would a user discover this feature?
