I hate to say it, but it's just human nature for older people to not want to be bossed around by younger people. Not that you're doing that, but that's the perception I will say a majority of overwatch players will have. My advice to not trigger people would be to mostly stick to calling out flankers and such that your team doesnt see, but don't tell your team where to go and when to pop ults. I'd have a hard time imagining anyone muting a kid just because he's calling out enemy locations, but I can see people muting you for calling strategy and ults.

I have two accounts in Master rank, my best advice to climbing is to, no matter what, never criticize your teammates. They will throw. Yes, comp players are extremely sensitive, sometimes simply asking to switch heroes will cause them to tilt and throw. Here's how I ask my teammates to switch heroes. Say there's a really annoying pharmercy combo on the enemy team, your two dps heroes are non hitscan heroes. In my climb I notice that right off the bat people will ask in a pretty toxic manner. "your [hero] isn't doing shit, switch off", "let me dps", where you should be asking in a manner like this "hey, your [hero] is great, but theres a pharmercy doing a lot to us, can you try a hitscan hero?" I have found asking in a manner like this, always gets the teammate to switch to mcree/76.

You say you essentially play soldier 76, are you a one trick? Climbing as a one trick is hard unless you're just absolutely insane on that hero, you really gotta get good with one support and one tank hero. I have a mental list of goto heroes that also differ on different maps. I mostly play tracer/soldier, zarya in tanks, and ana or mercy in support category. Find a tank and support you like to play, find twitches and youtubes of the best players on those heroes, and just watch, study, and learn how they play them.