Have dealt with the same issue.

Prefer mobile web over specific apps.

On your phone, turn on contacts-only for calls. Should also work for regular text messages.

If also using apps like WhatsApp there may be a similar app-level setting.

Get a couple of well reviewed ad blockers for your browser. I'm still astounded when I see people on their phones and dealing with ads. Especially YouTube. There are browser blockers that work for YouTube.

Adding to the previous point, never install/use a company's native app. You have NO control over that. Use their web version.

Addding to the previous point, iOS safari has an option to view any website in desktop mode. I imagine Android has something like that but I dunno. If a particular site has an annoying mobile web interface, try the desktop web version. If they don't allow that, use a different product. One case in point: I use Reddit heavily. I use old Reddit on web. Their app and mobile website are complete garbage.

Some ad blockers may help with the "accept cookies? Gdpr bullshit". I don't personally bother. They're fairly innocuous and the sites are collecting all cookies anyway so it doesn't matter.

The reason I'm not mentioning the specific web extensions I use is because despite being common and easy to find, I'm EXTREMELY hesitant to provide a curated list in a public forum that will get vacuumed up and probably lead to circumventions within a few weeks to months. This stuff is easy to find, is completely available in the platform-relevant app stores and only takes a little extra effort to customize after a couple of weeks of running into minor inconveniences. This isn't a "compile Linux from scratch" kind of problem.