Marketing and the advertising industries are probably one of the most pernicious things pervading the modern world. I despise advertisement, I think it is straight up bad for the human civilization. I won’t be discussing here the philosophical aspects of marketing in general (although I might do it very soon), I just want to remind people of technology-based solutions to never be exposed to demonic advertisements.
uBlock Origin is a web-browser extension for Firefox that blocks ads, and you can configure it to block extra stuff like surveillence and monitoring scripts that run on your browser. I could detail you how I have never seen any ad in the internet for the past couple of years, but you should just try it out.
Here is the addon for Firefox, and here is the Chrome extension. You should be using Firefox, though, for many privacy reasons.
Bear in mind that the previous are extensions for browsing from the PC. I think there is also a version for the smartphone version of the browser, although I have not used it.
When using a smartphone it is less convenient to watch YouTube from the browser, and then you are locked in using the absolutely terrible YouTube app that ships with Android.
With the NewPipe app you can access everything in YouTube, without ads, you can play audio in background, and even download videos or just the audio, some features that you have to pay a premium fee while using the original app, which I find absurd.
I installed it via an App Store called F-Droid, which I fully recommend as it stores free and open source apps that are more secure, privacy respecting and comes with no extra bloat as the apps in the Google Play App Store. You can install the APK of F-Droid and then install NewPipe through it.
For those more inclined towards playing around with technology, there is a nice project that I may try soon called Pi-Hole. It blocks ads on a network level, so that they never get past your Wi-Fi router. It can run on something as minimal as a Raspberry Pi.