How big of a disruption a kid is in your life really depends on what you were doing before having a kid. If pre kid you loved going to concerts, partying, travelling internationally, or other activities where having a kid makes it difficult to do the things you enjoy, then the kid might feel absolutely life changing.

However me and my wife are true home bodies whose hobbies pre kid were all either in the home or outside in nature or our garden. Having a kid made absolutely nothing we did before impossible, it merely made us have less time to do those things. The fact that my wife didn't work even before the kid also helped as I can imagine going from work to a 1,5 year parental leave as being a huge life disruption.

Having the kid absolutely changed our life in a major way. But probably far less so than it does to other people. And I would absolutely not say it was life ruining.