You might not have your Dealbreaker enabled for the preferences that you want to be 'hard' preferences (e.g. we never show you anyone outside those preferences.)
Unless they're set to 'Dealbreaker', we prioritize people who fit those preferences but also show you others.
To enable Dealbreaker:
Tap the preference you want to set to dealbreaker.
Toggle green to enable dealbreaker.
Tap to go back, and you should see the word ‘Dealbreaker’ next to the preference you edited.
The algorithm will automatically adjust your Discover queue to reflect these specifications.