There's a lot of "how" to give advice but not a lot of "what" kind of advice to give in this thread. Or maybe I missed it.

-Relevance is key. Why talk about lvl 70 rotations for a job when the only issue your drg in Sastasha has is forgetting to use heavy thrust?

-Try to be direct/specific. Falls in line with what was said above. Don't have to write a whole paragraph about your advice when you can say it in a few words. When it comes to explaining mechs, my rule of thumb is to explain what hasn't been encountered before. For example, the first boss in Sirensong is one I won't bother explaining anything as it has mechanics that has been usually seen in past instances. Compare that with say...Number XXIV in Castrum Abania and his Elemental Pillars. Its such a specific mech that can actually be really detrimental to the party if not done right that I do explain it. But just that and nothing else.
Now if the party wipes to everything, then I try to fully explain everything.

-Learn to actually let go. Guess what? Some people just won't give a damn about your advice. You already repeated yourself twice. Typing the same thing 3 more times isn't going to make them magically go "FINE MOM!" and do it. Chances are they just don't want to or...they don't understand the language/in another chat tab/too busy Netflixing. Either way, your just wasting mental health on being aggravated.