Even mechanically, the randomness in catan isn't brutal. Sure the dice play a large role in the game but there are many ways to
mitigate
the randomness. Putting all your settlements on 6's and 8's might seem mathematically sound but it means that you're getting your resources in big bursts while other players get a lesser but consistent stream that allows them to wheel and deal while you twiddle your thumbs waiting for that magic 6 that will give you 2 wood, a clay, and an ore. Not diversifying your numbers can make randomness feel more impactful.
You might also be undervaluing ports, I know I did when I was new to catan. It's another way of mitigating randomness, allowing you to change resources you don't want into resources you do. And finally, having deeper game knowledge that comes with just playing more games will also help. If there's a mountain and a pasture right beside each other with a 5 and an 8, and you confidently slam your settlement between them in the setup phase because 5s are good and 8s are really good, 4 turns later when you want to expand you are going to be thinking to yourself "man I need to build a road but I never get any clay, I'm having some bad RNG."
Knowing what resources are valuable in different stages of the game can help you manage your expectations regarding the RNG. and if all else fails, you can use the
Catan Event Cards (sold separately within the Traders & Barbarians expansion) which simulate a die roll but guarantee equal distribution because it's a deck of cards with evenly weighted die results on them.
THIS POST IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.