Happened,
Congratulations! She is someone else's problem now.

Please know, I am not invalidating your feelings, I suspect I would feel the same if my ex married my replacement. It sucks to be dismissed like we never meant anything. What I've learned though is it only hurts when you allow yourself to get stuck in that very thought:
I never meant anything.
Because that my friend is NOT true. You mean a GREAT deal not to just one, but several people in your life.
This morning I woke up crying. I am not sure why exactly. I don't normally awake emotional! I started thinking about all my interpersonal relationships up to this point. I come from a lower middle class blue collar hard working family. I didn't grow up on fancy vacations and designer brands... .we didn't have the money for those things, we barely had money for groceries. My mother busted her hump to send us to Catholic School. Luckily we had uniforms so we didn't need school clothes which would have been a luxury we struggled to afford.
I was a shyty student growing up. I didn't listen in class, was bored easily. I was and in many ways still am, a dreamer, a writer, a creator. My HS councelor told my mom I was lucky if I got into community college.
Somehow, someway I got through college, graduated and effectively worked my way up the ladder... .all with a pre-algebra education. I still suck at math but run a very successful lead generation program for a multi million dollar company.
Was it all luck? No. But I will say with honesty I had 0 support from my family when it came to education. I paid for college myself and paid it off in five years because I went to a state school.
Anyways, the point of all this was I woke up thinking about all the terrible crap people have said to me in my life. Being a little ten year old overweight kid with a bad perm and hearing my uncle call me a "little fat-ass a-hole".
Who calls a little kid an a-hole? Words wound.
You carry this stuff around with you... .and you carry it into your relationships. I remember all the times I was cheated on or told I wasn't good enough.
Ironically no one ever called me ugly or stupid but I was always pegged as weird or different because I had no friends and would play by myself on the playground.
I was the weird kid. I would pretend I was Wonder Woman using the tin foil from hot lunch as my bracelets.

As I cried I realized how all these words never really defined me... .
I let them. I chose to let them hurt me. I chose to let my ex's statements on how terrible I was become my reality.
I want you to go back and read outloud what you wrote about her new spouse. You tell me if that is something to compare yourself to? There is NO comparison. You are miles above that drama and garbage.
You didn't lose out. You FEEL like you lost out and that has become your reality.
You need to get very real, very introspective. I don't know if this is something everyone is capable of. Sometimes we don't want to work through the difficult and focusing inward can sometimes be more jarring than throwing the torches and pitchforks at our exes and their relationships.
What you see and what you hear are never the full picture. You know what it was like behind closed doors with your ex and I can guarantee that likely has not changed.
You have an opportunity to "reframe" your relationship with your ex. It's all within you. Instead of focusing on Why Him try to focus on Why Does this Matter so much?
I suspect once you get to the core of that question you will begin to see things much differently.
Please be good to yourself.