I think nurturing friendships is an important part of having a good life. I don't have a lot of respect for people who drop or start ignoring friends as soon as they get a new romantic partner for example. People with children should also make efforts to keep their friendships alive- otherwise they may find themselves quite lonely when their kids leave the nest (or simply start spending more time with their own peers), and they suddenly have a lot more spare time on their hands! It feels good to have ties to people you have chosen on purpose, and who have chosen you on purpose. It's life-affirming and enhancing.
However, I do think friendship as a concept tends to be a bit overhyped in Western society. You have all these TV shows about groups of friends who stay together through everything for decades, constant talk of "chosen families" being more important than blood families or romance... and in my experience that is simply not true to reality.
Most people's emotional lives are still occupied 80% of the time with romantic love ties, blood relatives and children. Friends do come, go and fade away a lot more easily than romantic partners, actually. I know a lot more people who are still together with their Uni sweetheart than people who are still in touch with a friend group from the same time period.
And friends are a lot less likely to be by your side consistently when things get tough. There are exceptions, of course, but largely I think it's true, simply because most people don't live with their friends, they live with their partners and families. Mumsnet is generally quick to advise leaving your husband, going NC with your family members etc, but I understand why many people are fearful of doing this, even in very bad situations, because loneliness is also very hard, and support from friends is generally just seeing you on a weekend and a phone call if you're lucky, while the rest of your life is left unmoored.
So I think it's also important to have a sense of proportion. Nurture and value friendships, but don't idealise them or give them more power over your life than they should have.