The stupid choice of strapline means this product will always have this kind of comment whenever it's discussed. Rightly so, IMO. It's the 21st century and someone would have to be a fucking idiot to not realise that this strapline is going to cause comment.
People eventually have to communicate, and someone is going to take offense no matter what. I think it's reasonable to expect people to start somewhere away from the worst possible interpretation.
The intended meaning is that your parents are less technically capable than you are; which parent is specifically chosen is simply not relevant. Would you have preferred, "Not your Dad's bitcoin wallet?" This is not sexist, it is ageist.
The best way to get people to stop talking about political correctness is to be politically correct. Pragmatically speaking, it makes sense to make a good effort to not offend people in your writing, since it detracts from the core message.
At some point there exists a line where you stop caring if people on the other side of it are offended, because they are nothing but a loud, vocal minority looking for a reason to complain.
I think that making an "ism" out of this headline applies. I don't know about you, but I'm not about to make language grey and boring just because certain people choose to take offense at anything and everything.
It's not ageist. It merely implies technology get's better with time. I can say "Not my dad's computer" and the implication isn't that my dad sucked at computers, its that computers sucked when my dad first got one.