It's like asking out someone on a date. If you have less experience, you'll probably do so in a dumb way and are more likely to seem like you're harassing them.

There's a lot of gaslighting that the line is aggression / assertion line is primarily about your internal state (mind reading arguments are often a good sign people are wrong), but the line is often about competence.

Pretending people should never be assertive means we aren't letting them develop competence except through experience. Developing competence through experience (without any clear direction) is like letting people learn to drive by letting them crash a bunch of times and learn from it which is hardly optimal.