It sounds like the coworkers are perhaps more knowledgeable in some areas, rather than necessarily having higher IQ's.
And getting to work with people who are more knowledgeable than you is exactly where you want to be.
Never be the smartest person in the room (unless I guess if you are trying to sell or buy something).
You need to forever stop worrying about your IQ. You will become happier, more capable, and more confident the moment you realize that your abilities, individuality, and worth cannot be reduced to a number calculated by a series of similarly formulaic logic puzzles. You don't have to be Einstein to make contributions to the world. When you are stuck thinking that way, there will always be someone smarter and more impressive and you will never be happy.
I advice you to read about Richard Feynman's way to learn. It will help you get past your perceived limitations. You should also read the book Outliers by Malcolm Gladwell.
Congrats on your job satisfaction.
So you're like 99% of developers then.
High IQ is helpful or maybe even necessary to build incredible things. However, many people with high IQs build regular stuff or even nothing at all.
Trust me on this, once you stop caring about it, the easier your life will be. Without anxiety and imposter syndrome feelings, you can focus on what matters.
Besides, high IQ is nothing if you do not have social skills, soft skills are just as if not more important to get things done and to be happy.
I wouldn't worry too much about that, there's plenty of great existing libraries you can learn to get the same results as if you had built it yourself anyway.
The problem is, I have a rather low intellect. My IQ is medium/low, so I am not capable of solving complex algorithms, and my brain processing power is nowhere near some of the other guys that I work with, so I can't build truly incredible feats of engineering like 3d rendering engines or voice recognition systems.
And yet, despite my shameful lack of smarts, I feel truly satisfied by my job, because it is the right fit for my capabilities. I build and fix UI's, have a fantastic manager, am supported by a positive and helpful team which practices positive communication strategies, and regularly get rewarded with compliments for my work.
I'm not a big fish swimming in a small pond, nor am I a small fish swimming in a big one - my pond and I are in balance, and there are no sharks or parasites in it, and that keeps me happy every day.
Please God one day they will invent a therapy that will give me Einstein's IQ. Until then, this will have to do. Hope this helps.