My CMDR is doing this right now.
Just the other day, I actually managed to get my Viper shot down by ATR after killing two dozen system security and had a laugh over how I was immediately back in action after paying a measly 1.5 million CR fine...for the murder of dozens of police and inflicting billions of credits of property damage.
The notoriety is barely an inconvenience and disproportionately lenient relative to the crime.
And yet, that's
still more difficult than what it used to be

Not saying I disagree with your sentiment.... my point is just it's not "hard", just "harder".
Anyways... quoting myself ftw:
EDIT: Have some other things to add in a bit which you might find interesting, but I can't post for a bit.
Can actually write again now (obvs)... and here's the thing.
Like I said, and you ignored, can kill 10 million NPCs in anarchy systems and nobody bats an eyelid.
Kill 10m NPCs in the right system at the right time and
everyone bats an eyelid... and there's a
whole subforum of people who care about NPCs and what happens to them.
I think you're missing the point why killing NPCs arbitrarily earns you notoriety... thing is, your issue has some merits, but removing notoriety as it currently functions from killing NPCs isn't one of them.
One of your problems is that you winged-up with someone who was running missions to help them with them, without actually having them shared with you/were non-wing missions. I personally think there's a strong argument that wing missions
shouldn't exist, and mission rewards/conditions should just be automatically shared among wingmates. That would actually have fixed your problem entirely as they would've been mission targets and not just random NPCs.
You have general problems with Notoriety. While it should have impact on continued lawful conduct, it should have benefits when it comes to the pursuit of further criminal activities... something which I wrote about here:
https://forums.frontier.co.uk/forums/elite-dangerous-background-sim/ tl;dr "Good people" should be able to wash themselves of more minor crimes (which yours wasn't really...) while "bad guys" have new doors open for them at certain levels of notoriety, which could've been interesting for you.
In other words, there's an imbalance of "Crime" against "Punishment" right now... but you don't fix that by reducing the punishment, you fix it by increasing the rewards of crime. Borrowing Mangal Oemie's chart...
That's over 6000 positive economic states versus a couple hundred negative ones, and 1700-odd positive security states compared to a hundred negative ones, and no instances of Lockdown or Famine in the universe at that time. There's again a significant argument that the game needs more incentive for negative-effect behaviours, but removing the punishments isn't how you do that.
So, yeah, I think there
are problems which brought us to this point, but the fact you got notoriety for killing a bunch of NPCs not relevant (in terms of the current game mechanics) to your activity isn't one of them.
Like your topic says... "Notoriety is no fun"... I can get behind that... but that's not fixed by making you receive notoriety for pointless criminal acts.