I think, besides the obvious "adults shouldn't date minors," anything else should be legally allowed. however, when two people are in different stages of their lives, that's where power imbalances and exploitation of one partner's inexperience are more likely to occur. I feel if you date outside your life stage, you're either putting yourself at an advantage or disadvantage, and vice versa for your partner. this gets worse the bigger the age gap - and it can be counteracted, but only with awareness and intent.

and of course, "life stage" is hard to define. but if the other person has never worked while you have a decade of experience in the workforce, if you've had one short term relationship while they've had a divorce and kids already, if you have 10k in your bank account and they own a company and property, I think that's hard to build a healthy relationship on. experience is everything.

in your 20s, so much changes and experience compounds in such a relatively short time. I think a 27 year old like myself dating a 22 year old would be a huge stretch, but a 35 year old dating a 40 year old is not. that's because with a 22 year old, I've already been an adult over twice the amount of time they have. but for the 40 year old, they've only been an adult 30% longer... if my math is right. make sense?