I think the attitude is often because of the stereotype of the man leaving his wife and children for a younger woman - so emotions are already higher because of the situation, and the wife obviously finds it a kick in the teeth for her partner to get with someone who is much younger than her.
It's not always like that. My grandparents had an age gap of 20 years and they were together for decades, until my grandad died last month at the age of 96. They were an amazing couple, and so incredibly happy right until the last day.
My partner is 21 years older than me. I have always dated older men, but not that much older. I didn't seek him out, and he didn't seek me out. We have a shared hobby, and met through that, and started talking. We clicked, started going for drinks with a group of friends, eventually started going out alone - exactly how you would expect to get with someone your own age. My family and his were definitely wary about the age gap, but for us, it works. The only thing I worry about is that I could be left on my own for 20 years when he passes away, but to be fair, I could die first, there's no way of knowing.
We have been together for two years now, and live together. This relationship is much better than any other I've been in. We run a business together, have a shared hobby (along with separate ones, so get time to ourselves too) and enjoy evenings in watching TV - we like the same shows!
You just can't put an age on love, nor should you try. Okay, so sometimes there are barriers that become bigger as time goes by, but not always. For me, it is not about power or money. I have a better paid job. He is not well off, he won't be leaving me anything when he passes away, his house (which I live in) will be given to his son. I am fine with that.