Others have written it more eloquently, but as someone who shares a lot of your tendencies and understands where you're coming from, please don't give up solely because of this. I am 100% pro-choice but as a friend once told me, this is a permanent solution to a temporary problem.
Online dating can be demoralizing, doubly so for us guys who are often expected to do all the work of initiating and overcoming the mathematical disadvantage that we have online. The tendency to compare yourself to others is always right there, and it is easy to reach for a simple explanation like looks that gives a neat explanation for the pain. Looks do make things easier but as someone who developed male pattern baldness at 19 I can tell you that they aren't everything and acting as if they are is a cop out. If I killed myself then I would have missed out on the love of my life. If you had a 4 year relationship at 23 you're way ahead of the path I followed, and I would further argue, most average people.
Losing a relationship is always awful and all of the worst depressive episodes I've had have followed breakups, but if that is the only major issue in your life it is very fixable given time, work and patience, especially in your 20s when your dating pool is so huge. If you want a silver lining, it's that if you aren't a 10 you won't have to filter out the girls who only care about looks. You don't want them anyway. What matters is finding someone compatible that actually loves you for you and not something that will fade in a few years anyway.
If you take the advice given to you earlier in the thread about cultivating your hobbies, taking care of yourself, and finding meaning in your life outside of finding a partner it will pay dividends. Not only will it take some of your focus off of a woman being the only answer to your happiness, it will put you in a much better space mentally, and it will be much more attractive to future partners. Someone being obsessed with you and having no life of their own is not attractive, and I say that as someone with that tendency to love hard myself. Live your life, figure out some things that matter to you and motivate you aside from women, and they will come.
As to the dating apps it's a slog, but you have to just toughen yourself mentally and realize that most women are not going to message first and the most desirable ones have 500 guys all messaging them at once. Make your profile a true representation of who you are and not some curated bullshit, don't pin your self worth on the apathy and cruelty of strangers, and just refuse to give up. The one you find after 100 bad experiences will make it all worthwhile. Good luck out there.