The unspoken assumption in all this is that you are obviously correct and your partner is a moron.
Exactly.
If you are obviously correct AND your remarks are truly about strategy and tactics, then you will have no trouble leading by example and by using "we" instead of "you."
Think of it this way. Saying "you" should do such and such is inaccurate, isn't it? You're a team. You both have to execute the correct strategy. So if you struggle to talk to your partner about what "we" should be doing, then you probably are being critical.
In some cases that may be correct, but you are seldom the best judge of that, particularly in the middle of a frustrating match.
Exactly, again.
No one here has said you cannot confer with your partner about strategy.
But it is not appropriate to make unilateral declarations about what your team strategy should be. You both need to understand what is happening on court and what you might do about it, and you need to agree.
So. Instead of telling your partner not to hit through the net player, better is to have a discussion about where you will both hit your returns. That's not criticism. That's communication.
It's just that it's such a thin line from that to your partner feeling they are being micromanaged by someone who is not that much better than they are. The last thing I want is my partner freezing because he or she is worried I'm going to criticize them.
It can be even worse than that.
Say your partner has missed a lot of returns. Say you march up and say, "Come on. Get your returns in play!" What is the very next thing that happens? The player who said it misses a return. And the partner immediately thinks, "You're no better at returning than I am, so get off my case." This is unhelpful.
Regarding whether this is a gender thing or not, I have no idea. I play 90% of my matches with women. When I play with men, I don't criticize them no matter how horribly they are playing so I don't know how they would react if I did.
I do remember overhearing a conversation between two male teammates when I played 7.0 mixed. They were laughing because one of their female partners had the audacity to tell him how to play. I guess her criticisms were not appreciated by the menfolk.