If you're going to approach focus like an engineering problem, you probably want a minimax strategy: figure out what keeps you functioning/healthy and devote minimum adequate focus there, figure out the reward space you want to explore and devote near-maximum resources there. And leave a little bit of slack baked in for when attention is overscarce or for when you need perturbing input. Digital distractions can be that slack. Or they can be your dump stat (he says, while posting on HN :/ ... ).
Most people will find that a handful of close relationship plus some web of weak ties fit in both the "keeps you functioning" and "reward space" categories. Which both underscores the importance of relationships, and the challenge: you are probably going to have to balance frequent not-especially-rewarding maintenance work, and regular (but longer period) reward-space exploration, and feeding slack time to it.
Also, for me it was more important to understand what NOT to focus on. Figuring out that which truly does not matter and letting it go is one of the most freeing things I have done. It's also a skill/tactic I see at all levels of life. The big picture of your whole life, then there is your work life, then there are work problems, then in jiu jitsu, etc... And the funny part is that people know bike-shedding exists and still do it day after day.
In other words, it is better to be alone, than with someone who ruins your mind and sleep.
So from an evolutionary standpoint, focus might not be that important after all ;).
Most people make mistake they start compromising very early for no reason, and when things get tough, they just get buried.
Because if I've learned one thing in my life it is that there is no sex without a relationship. Everything else is a sliding scale of masturbation.
The desire to pretend otherwise is a cause of significant misery for many people.
Also no man is an island. If you want to make that spaceship to Mars, you will not do it yourself. So that advice of cutting off ties in order to improve focus is terrible.
A better wording of that advice would be to re-focus on important and strategic relationships which benefits you and vice versa.
It's healthy to know we're only human, and we should strive to build a few quality relationships that don't interfere with our life, and knowing when to say no otherwise!
Our relationships are our life. Our goals are just stories we've made up about ourselves
Even though it's good to value friends and family (not arguing against this at all!), me time is needed too. Hobbies and other work you like.
Personally I believe there's a good amount of engaging with your acquaintances, and an excessive amount where you're just shuffling around between them, getting lost in those dynamics. In that case, there's probably a way to keep relationships growing naturally, with almost the same returns and much less time sunk.
What good is it to gain the whole world but have no one to enjoy it with? Of course this is simply another form of focus - choose which relationships to focus on. But putting intellectual pursuits above relationships is a lonely and foolish path, even if you achieve your dreams. If someone close to you suggests spending more time with them, you would be better served to listen to them than to cut them out of your life.