I agree with you to a point. "could I get a better mate" is absolutely true when you can swipe across hundreds of profiles.
Where it is not true is that attraction is a multi-dimensional process that is very poorly captured by online dating. Men in particular are disadvantaged by it. This is well studied.
The false conclusion to draw is that if you fail at online dating, you will fail at real life dating. This false conclusion stops many young men from even trying in the real world. There are so many dimensions on which attraction is developed that many, many who are currently alone could easily and successfully find partners. It makes me sad.
I have absolutely seen 5'4" men who would catastrophically fail in the online dating market meet, date and marry successful, intelligent, kind, beautiful women. I have absolutely seen many nerdy men, goofy men, brown men, asian men succeed effortlessly with women. It all requires real-world interactions though.
In the real world, people respond to so many more signals. You have to go out there, meet people, learn and develop yourself.
This is the process I encourage my single friends to follow: become the person someone else would be thrilled to meet, proud to befriend, excited to date and overjoyed to marry.
But to do so, you must first go out in the real world and make friends. Don't go out with any expectations of getting a date or a hookup. Learn to make friends with a diverse array of people. This is key. Each different type of person will help you learn about yourself.
Dating will emerge naturally as you get beter at making friends.