You are not synced in the following content:
- Max level trials.
- Max level extremes.
- Max level alliance raids.
- Max level normal raids.
- Max level savage raids.
- The latest expert dungeon or two.
- Max level maps outside, often inside too.
- Last zone's FATEs.
- Hunts.

You are only synced, mostly, if your hobby is doing roulettes that throw you into sub-100 content. If you avoid that, your gear mostly does affect how much you destroy enemies.

Granted, a lot of people see old roulettes as their main content, but if you're really burned out by the concept, you can mostly solve it by avoiding sub-100 roulettes.