I'm actually surprised how they could cause problems? Do you have specific examples?
1) use uMatrix and block all scripts and all third party sites
2) go to your favorite bank
3) if you're lucky, you'll get a warm welcome to enable javascript. i don't think that's reasonable, but just enable it to get moving.
4) after enabling javascript, see a few third party sites. some of them are "content delivery networks" (which IMO shouldn't be a thing, and absolutely shouldn't be a different gTLD), some of them are telemetry (hope you trust your bank to vacuum up only what they want), and some are services your bank tries to upsell you on (please sign up for our (third party) rewards to further monetize your purchase habits).
5) good luck trying to figure out which sites to trust