https://www.mensjournal.com/features/everything-you-know-abo...
Parent might be referring to the assertion that the abs' main role is to prevent torso flexion (as opposed to cause it), which makes something like a Paloff press a more 'functional' movement.
Strength training helps with you meet the demands of the things that happen irregularly like moving furniture, clearing snow, having to take care of an injured spouse or parent, or even just playing the odd game of [sport-of-your-own-choosing].
It counters the atrophy associated with a sedentary lifestyle and delays the physical decay associated with old age and adds life to your years. It strengthens bones and improves body composition.
It makes everyday life easier and would be worth of billions of dollars if its benefits could be captured in a pill.
You are wrong. It puts undue stress on the knees, even with low loads. I've had 3 knee operations (on one knee!) so I've been through a lot of PT. Open-loop exercises should just be avoided. Their closed-loop counterparts are better/just as good.
You sound like you want an argument. I'm not interested. I am proud to say I am a relative newcomer to proper strength training. I can say that your arguments do not agree with anything I've come across yet, but hey, if it works for you, go for it.
Crunches are overemphasized and should take a back seat to exercises which train your real core muscles. Most people don't need them. They need a stronger posterior chain, obliques(and all the little core muscles), back extensions and training on proper breathing.
Similarly, let's talk about 'functional ab muscles.' Functional is a needlessly vague term. Let's say I'm a powerlifter and I feel my core is limiting my squats. Don't tell me to squat more, because I am an advanced squatter and my core is weak despite heavy squatting, so clearly it would benefit from more direct work. How would you strengthen my abs so my squat can improve? Outside of extremists, most coaches supplement auxiliary lifts to improve weaknesses.
For what it's worth here's a video of Konstantinovs (800+lb deadlift) doing crunches, I don't think he would do that unless he found 'functional' value: https://www.youtube.com/watch?v=vMjXVHHAJ70
I appreciate your enthusiasm but it sounds like you're very clearly a beginner and in situations like this you should keep a more open mind and avoid judging so quickly.