A surprising topic I've given much thought to.

I think online relationships are destructive forces. The function of a conversation is to employ a process to somewhere - but when the function itself is the process, then only one thing is guaranteed: disappointment.
What I mean is that if all you can look forward to is further correspondence over mutually exclusive lives, it is easy to feel even more alone than before. Relationships are vectors where one shares experience. Some may take this as a conversation, but there is a backdrop within these dialogues. You may be walking around a city, or eating in the park. There may be a festival to attend, or a board game.
In online realms, there is little memory to weave together; there is little to bask in if there only are diplomatic islands disclosing what the water is like on their end.

Social functions are far more than words. A fact somewhere states that around 80% of our relations take place in body language. There are many nuances that simply cannot be shown in texts or voices - goes to show just as OP mentions that they have lost so many people to inane things that a simple expression could clear up.

Not only are these things lacking so much on the connection front, but also these things chip away at your personal time in the form of notifications. Inevitably, it is quite rare to report on anything else BUT the state of the water. That is, the exploration of the other, mutually, leads to an end. For rarely does both in correspondence take time to actually live. The lifestyle necessary to entertain online relationships usually, through unfortunate circumstance, calls for a benign half-presence. This means a lack of personal growth, and a limited view of curiosity. It is often why many people shed themselves of so many others, for it's unsettling to be even remotely aware how much stagnation has taken place for either party.

In the event both in correspondence do take time to live, it then seems inevitable to notice how online communications hurt their full-presence lifestyle. To always be in finger-reach evaporates things to catch up on. It makes things confusing. When do we get a break? Where is the divide between friends and myself?
Either one becomes hard to reach and hurts their online friendships, or gives up in being in the world and double downs on finding a quasi-fulfillment in talking about the water for the hundredth time.