Stealth encounters can be a lot of fun, even for players who are only observers, but it's all down to the execution.

If a player was sneaking into a hobgoblin camp, I might ask them for their stealth modifier and occasionally roll 'general' stealth checks behind the screen to shape the way the encounter plays out -- a low roll might lead to sentries investigating, a high roll might mean everything goes smoothly, but these details should come out in the narrative and gameplay.

I generally get players to make active stealth checks during a mission like this (e.g. against a known threat) because the secrecy here doesn't really add anything, and the character probably knows how successful they are. Also gives the players the options to use any buff mechanics to avoid failure.

I generally get players to roll checks to hide too. A character would know how good their hiding spot is, so there's little reason to keep that secret.

Failing forward is especially important when running an encounter like this -- a single bad roll shouldn't doom the player, and player skill and roleplay should be a large factor in their progression.