Of which they're accountable for. Are refs?

Yes.

Not even nearly as much as a player though. If a player made as many mistakes as some refs, they'd be dropped the week after or get subbed.

Only if the team had a better player waiting behind him.

Yes!!!

But not to the likes of you and me, just like the players.

?

If there was a better player, why would they be waiting behind him? Surely they'd already be in front of him?

If there was a better ref, why would they be waiting behind him? Surely they'd already be in front of him?

Perhaps the coach thought the starting player was better until he saw him make all those mistakes you posted about.

Or maybe fancied giving someone else the chance to develop and prove themselves and send a message that such incompetent standards would not be accepted?

No. Coaches never put someone out there just because they "fancied giving someone a chance"
Those chances have to be earned through training, and playing at other levels.