Obviously it’s going to depend on the setup, but doors aren’t a seal, they’re just blocking the water from getting out. If there’s still a lip at the bottom even with the door gone to keep stuff on the floor from flowing out of the shower, a curtain can work. My family had to take out the doors and put up a curtain in my mom’s shower to accommodate things like her shower chair and nursing aides after she was severely injured in a car accident. It worked just fine. Given how many different setups are out there, I’m sure there are circumstances it won’t work, but it is workable for at least some shower layouts.