Have to agree with this. It sounds bad to say it out loud but the general internet populace is unfortunately comprised of a cocktail of self-interest, anti-social behaviour and anxiety all in varying amount.
Approaching someone with topics that interest them are the best way to really keep conversation. The key is to maintain interest so that you can, over time, overcome the barriers many (including myself admittedly) have put up over the years.
I'd disagree about the internet community and people in general being anti-social, though sometimes that is a factor. Most people want to talk and enjoy some company at least some of the time. The problem is they might not be the best conversationalists, which can stall a lot of conversations. People might ask awkward questions or bring topics that the other person might not want to discuss with strangers. You, generally speaking, also can't expect to talk mainly about what you want to someone you just met either; on the internet or in real life, that will usually turn people off because most people want their say to be heard too. It's got to be give and take.
You need to be willing to talk about what the other person wants to and you need to listen to what they have to say. Both those things are life skills and they're important to remember anytime you meet or talk to someone.
There are also a bunch of problems particular to having conversations on the internet that hamper talking for long as well too, and I feel these are probably the most likely reasons talks get cut short.
1. Most conversations on the internet are typed out, not actually talked through, and a lot of people hate writing in general. It's easier to talk on a voice call because ... you're just talking and almost everybody find that easier that talking. Now, a lot of people don't want to talk on voice calls for decent reasons shyness, privacy, or background noise, so that isn't always a viable alternative to text-based messaging. That is part of reason I prefer voice calls with friends when I can do them, but a lot of lean towards text because it does have benefits. For instance, a person doesn't have to be on for them to receive your DM and it's easier to carry on multiple conversations at once via DMs that via voice or phone calls. It's also easier to DM people you're on mobile and or doing other stuff.
Another problem with text-based messages is that people tend to organize their written thoughts differently than in a free-flowing conversation, which can take more time and effort. They also may not talk about certain things that they would effortlessly in a spoken conversation.
2. If you're talking to someone on the internet, you need to cognizant they're probably doing other at the moment as well too and not sitting in front their computer typing. Like, I'll admit that while I'm DMing at home, I'm at least talking to one of my housemates in person and either doing house stuff, reading, streaming, or browsing which draws away my attention. Sometimes I talk to people during mini-breaks or lunch breaks at work and I have to ghost, which I get complaints about, justifiably. With pandemic, a lot of my friends are on Discord and Duo now, so it can be overwhelming to keep up with everybody too.
I'm sure other people similarly have to deal with real life situations that draw them away from online conversations as well and we need to recognize that everyone isn't available to talk all the time, but it might help to explain to people what is going on in your life too, they know you're not ghosting on them. I try to do that as much as possible, but sometimes I don't have the time too.
Others run into the same problem too.
3. Since we're talking about conversations over the internet, it's worth pointing out that people can be cagey about talking to strangers on the internet, especially people who aren't men, because people can be creepy on the internet. Using a microcosm we're all familiar with, I've had female friends on here who have got spectacularly creepy messages here from total strangers which put them off talking to people they don't know and made them lock their DMs. It's a problem on a lot of platforms and women tend to more careful than men about who they talk to, for understandable reasons, and guys could be sensitive to that.
4. Another thing I've noticed here, and I'm not certain I'm going to get this across well, is that a portion of people here want serious and fulfilling conversations ... but don't talk in a manner most people will find serious and fulfilling. Like, I see in Last Post Wins and the other chat threads that users joke around, roleplay, and speak in a playful and childish manner, which is fine for the thread and this is a furry forum. But while that kind of talk and roleplaying can be fun in short term ... you can't really expect people to carry on with it forever, especially if you want to laid the foundation with conversations for a lasting friendship, which I'm this is thread is really about.
This isn't to say that serious conversations don't happen here; in Vent Thread and DMs I've had some real talks with people and I've seen conversations here where people have been serious and supportive of each other. But if you're talking to someone via DMs and you're speaking like a second grader, roleplaying constantly, and unwilling to be serious and hear them out about real shit ... you can't expect them to hold up their end of the conversation. It's give and take.
I don't really know what else to add, so I'm just ending here.