Online friendships are just as valid as offline ones. Anyone who says otherwise is full of themselves and full of crap.

I think online friendships are different from offline ones.
It's not a matter of validity, or even value, it's a matter of how you are present.

Online friends can't give you a hug when you need it more.
On the other hand, it's often harder to have a long deep conversation offline - specially if your interests are quite specific.

Yes, of course, online friends can fill an important gap if you have no offline friends.
Even if you leave the house, even if you have plenty of acquitances, you may have no real friends to whom you can tell things, with whom you can discuss things.

I can count the number of people I consider dear friends on one hand. One is someone I've known since I was in high school, two are people I met at my first go at college, one is my partner, and one I met at a Transformers convention.

now, outside of that circle, I've got many more friends who I sometimes get to see in person.

The rest of my friends are people I've met online.

I have so many friends who I want to be able to visit, but can't atm due to the state of the world and my own financial situation.

They want to talk to you because they want to reconnect if you've drifted apart. If it's someone new, it's because you seem like someone interesting to talk to, or they can relate to you.