Gumshoe doesn't guarantee you will solve anything. It guarantees you won't miss the necessary clues to enable you to make decision on your courses of action, be that to solve a mystery, or expanding the model, approach the negotiations table with the most pertinent facts, or decide on how to best wage a war given the current situations.
The particular model GUMSHOE has breaks the typical rolls run everything approach many games have. This "universal approach" isn't, there are many many ways players and GMs modify that approach to suit the actual results they want. Allowing only one roll or many, one chance to find info, or many, requiring rolls to interpret something or not, allowing player decisions to overrule (or not) what the dice say, the ways to customize a roll are endless. Many weigh the results towards many rolls to fail, or many rolls to succeed without realizing it.
If you are trying to break the usual way the game system runs things, you usually look at what the players do that is FUN, engaging, and that enables RP at whatever level (from in character acting through narrative to basic table talk description of game mechanics choices) and focus on getting to that, and making IT more important.
If you want a pure sim, you will end up with the muddy results of reality, and a lot of dead ends and unresolved events, and you'll get to play through every unrewarding hour of it. I love nodding to those realities, but I want to get to the stuff that is interesting for my players and I.
There is a page in Powers: Who Killed RetroGirl? that shows frame after frame of legwork. It gives the nod, then the story moves on. That's what Gumshoe is trying to, except instead of summary of many non-interesting but necessary events, it's about moving quickly through the parts that won't lead to interesting stuff in a game system.
Imagine making an alertness check, a perception check, and empathy checks every single turn of a game to represent your actual perception of everything. Could lead to awesome moments, but most likely it leads to a million rolls we fear are needed, but never go anywhere. Best to roll when the situation is complex, more complex than it appears, or MAYBE when it might highlight your characters shortcomings (like they hate the Irish).