Lynel are a "skill wall" where you have to learn dodging to pass them. Once you can dodge and hit back reliably, they become much easier (still hard, but not impossible)

Lynels are intimidating but aren’t unmanageable after a few encounters. Mostly they’re just annoyingly consuming weapons. On defense, upgraded armor, stasis and actually USING the shield is good enough. For offense, urbosas fury + mount and strike gets most of the health down. Bonus points for flurry rush.

Hope you pick it up again, if you’re at the castle you probably don’t have too much left.

Using the glider to chain critical arrow shots is a great way to take out a lynel quickly, too. There's only a few places where lynels appear where you can't use that tactic.

Lynels really annoyed me because there was such a big skill jump between them and everything else. I saved close to a Lynel and practised for several hours to get the hang of dodging. Once I nailed that, they became much easier. Then you just keep the weapons they drop to kill the next Lynel, since they're so powerful and durable.

No lynel is mandatory. The castle ones (there's two) you can skip by climbing the walls instead of entering their "arenas".

Think of fighting a Lynel as if you were fighting a challenging opponent in Punch-Out!, it's all about timing, and once you get it done not particularly difficult