The 'Hard' tag on dungeons and trials is a somewhat misleading holdover from an earlier time in the game's life. Really they're just higher level remixed versions of lower level dungeons (and trials eventually dropped the Hard tag entirely.) That said, as a new player who's still progressing the story you can ignore all of those dungeons for now. They're not required and will still be there later if you want to go back for them.

People blazing through and blowing up everything in seconds is an unfortunate side effect of gear progression at the old level caps (50/60/70/80.) Story dungeons like Praetorium or Crystal Tower need to be doable by newly 50 players in low level gear so of course they get instantly crushed by veterans wearing i130, even with the level sync in play. You'll stop seeing that quite so much once you get into the expansion content though. The devs learned a lot from ARR and started designing dungeons and syncing gear down differently afterwards.

Trusts are only available starting at level 70. The Trust system lets you do dungeons solo with NPCs filling out the other party slots. The system wasn't added until Shadowbringers so it doesn't apply to you as a new player still in ARR.

You will never need, or have anyone expect crazy gear and a video watched before doing normal difficulty content. If you're trying to do a current tier Extreme trial or Savage raid, sure, but while leveling or even when doing normal mode endgame content, as long as you meet the game's built in ilevel requirements (which are usually very lenient) you'll be fine even if you go in blind.