There's no such thing as "just right" or "too hard" or "too easy", just as there's no "too sweet" or "too spicy" when it comes to food - it's all down to an individual's own tastes.
But what there
IS is
a proper frame of reference.
Someone brought up in Thailand has a very different view of "too spicy" compared to, say, someone who grew up in Finland. And likewise anyone who's drunk a can of fizzy soda from India knows that Indian drinks manufacturers have no concept of "too sweet" at all - that stuff is 100% sugar.
Point is, for folks who've been brought up on space combat games, the perception of "too hard" or "just right" is
automatically skewed because of our long experience. Same goes for the folks who
develop such games, and who are by necessity exposed to space combat day in, day out.
But for new players, casual players, and those who enjoy space combat but just can't get the hang of it for whatever reason (including physical limitations from injury or disability, etc) it's exactly the same as someone who's never tasted curry before suddenly being presented with a bowl of vindaloo and being told the heat is "just right"
And then to have someone laughing and saying "GIT GUD" at the person who's just burned their mouth on a curry they were assured wasn't hot is just crass and boorish, and does nothing to promote our beloved game to more potential buyers.
In pure game terms, it's financial suicide for a Harmless player to be interdicted by a Deadly NPC and insta-shredded. It would be like a dragon suddenly jumping in and stomping level 1 players in the n00b zone of a game - it just doesn't happen in MMOs for
exactly that reason.
If new players choose to fly into an Anarchic system, then all bets are off - just as in any MMO if a level 1 can wander into a high level zone, the first critter they meet will nom their face off. But in high security systems, low combat ranked players should
NEVER be interdicted by high-rank NPCs - it's as simple as that.
For low combat-skilled players, the AI of low rank NPCs is just fine. And before anyone says "Dur dur, game realism, why can't high rank NPCs interdict low rank players dur dur..." I would stress that word
"game". As in this is one. And one where we necessarily have transwarp escape pods and cargo that teleports into our holds at stations. We all left our reality check coats at the door when we came in you see, because - shock horror! - this is
a game.
And games need to be bought.
And people won't buy a game they've been told has a vertical learning curve.
--------------------
TL;DR
Basically, if the combat is a bowl of vindaloo from day one, people won't buy it.
And if there's no way players can control the difficulty of the combat they face, they'll simply stop playing.
But if random encounters are matched, so that the random interdicting NPC's rank cannot exceed the player's rank in non-anarchy systems, everything will be golden.