Would you abe able to elaborate on these two things ie (1) your rules changes and (2) how their PCs have revealed themselves to be bland and ineffective?
The only CoC I've played recently is Cthulhu Dark, which (as the name suggests via word-play) is very "lite" with a simple but (as I've experienced it) effective resolution system and rather colourful PCs.
Yeah I remember you talking about Cthulhu Dark. I have a copy as well.
We left Trail of Cthulhu, the italian edition, translated, waiting for ages on the shelf, and I've been asked to run it and see how it goes.
Well, first off, let's say a Pc starts with a Profession, and has three main status indicators: phisical health, emotional balance and the usual sanity-vs-mythos-awareness.
So you could have an expert on mythos (almost non human anymore intellectually ) with a strong focus, mental balance, reason; otoh a completely occult ignorant on the verge of madness, irrational personality wise.
Pc is basically made of Skills; these are expressed as a number (of points): Archeology 4; Firearms 8; Intimidate 2...
Skill are divided in Investigative ones and General (action/non-investigative) ones.
Investigative skills don't roll dice for resolution: if you use the right skill (or a reasonable different one) in the right place, you get the core clue (if present of course, or if the gm improv it).
Points from the skill can be spent to get additional info (if any): that means spending more time and effort in the fiction, sometimes.
These points spent never refresh during the "adventure".
General skill, on the other side, mean failure is an option, so you roll a D6 with a target number ranging usually from 3 to 5. Points can be spent to raise the odds, or downright meet the target number without bothering to roll. These points do refresh once in a while.
Ok, thing is: Combat by RAW is resolved in the most traditional way. Sides takes turns, roll to hit, difficulty depending on opponent ability, roll for damage, add weapon damage modifier, check health, repeat, eventually see how much health goes below zero for stuns, injuries or death.
What I did is, for now, to simply reject the above and just declare what someone is doing followed by another declaration by the opponent. Points can be spent to make a declaration stick in order to gain advantage, or any else fictional positionong to alter the scene. Eventually dice are rolled by the Pcs when it seems appropriate, or to end the combat.
eg: a Pc wanted to spend a point to intimidate an opponent when both had already raised their guns against each other: this allowed the PC to fire first, then he had to roll a die to see the outcome: miss, injured, etc.
When a Pc must defend may spend Health itself to roll for... defence

So I changed health from status to actual skill.
That's basically it.
I have a look at opponents Stats (when provided) to use them descriptively, but I don't roll dice as Gm.