How to launch `.desktop` files from the terminal (or dmenu)

I want to run .desktop files from the terminal and dmenu. From the terminal, it should ideally be run with ./app.desktop or /path/to/app.desktop, and app.desktop would be put in a $PATH directory. I'd rather not have to use an external command like gtk-launch app.desktop. Additionally, I've found that gtk-launch doesn't always work to launch the application with gtk-launch app.desktop, and even when it does work, putting #!/path/to/gtk-launch at the top of the .desktop returns the error gtk-launch: no such application ./app.desktop when I run ./app.desktop with it executable. I'm using bspwm and generally prefer launching things from the terminal or with dmenu_run so I don't have a desktop from which I can click on the .desktop files to launch them. How can I make the .desktop files executable?