Even though D&D is a fantasy game, it uses our own world as a starting point. In the real world men are stronger than women. Significantly so. This is a
fact.
So if we want to model human men and women in a fantasy game then on average men should be physically stronger than women there as well. That would be the baseline. But there is no reason to limit character abilities according to gender based on reality.
Back when my group still rolled stats we had different modifiers for male and female characters, but if you wanted you could roll the male stats for a female character or vise versa. It was really no big deal. It did mean that females were generally smaller and weaker than men in general, but they had other physical advantages (usually a bonus to Con or Dex).
I think the same goes for races. There are no Halflings or gnomes in our world, but small people are, obviously, not as strong as bigger people. So since they are small, why should they be as strong as humans? Why shouldn't elves be more fragile and dwarves slower? At least on average. Sure dragons can fly in D&D and according to physics they shouldn't be able to, but why does that mean that halflings should be as strong as dwarves?
Now while I have seen strong women and intellectual half orcs played strait, I have honestly never seen a halfling with an 18 or higher strength that wasn't a joke. The entire game the character would be laughed at as they lifted heavy things or did other improbable feats of strength. Now if you are playing a beer and pretzels type game where nothing is serious, that is fine. But it really detracts from a desperate, save-the-world campaign if Heman the Halfling stops to hit on the Marilith by flexing his muscles at her.
All that said, currently I don't place any restrictions on characters. But I do keep default assumptions in place. Generally human men will be stronger than human women, with notable exceptions. Small races are weaker than big races and races with specific stat bonuses are superior in those areas. Then I just rely on players to keep those things in mind. If they want to defy those expectations I just ask them to put it into their backstory. If the reason is simply, "because I thought it would be funny" I make sure the rest of the group is on board. The whole point of the game is for everyone to have fun (including me), not so one person can have fun at everyone else's expense.
tldr: Hard min/max rules are a thing of the past for good reason, but they can still be good guidelines to represent the norm.