I would focus more on getting a new or newer phone than on pointless conspiracy matters -- i.e. the Apple incident was a very selective one and just old news, not unlike the silly rumors about Samsung is failing because of its Note 7 battery incident (i.e. smartphones are just a small part of its business and it's still selling the largest market share of phones). Also a selective matter and old news.
But here in the real world, it's still a matter where a dated phone like your S5 has just aged to the point where its usability has diminished. Google stopped supporting it a long time ago, most app developers too so even the apps on it are in question, and basically there are hardware limitations that will make even third-party ROMs more about just having a phone that boots up than a phone that's actually usable as a daily usage phone again.
Today's Internet has devolved into a toxic mix of really useful online services and countless compromises so using any outdated mobile device involves an increased amount of risk. Keep that in mind as you want to keep using your S5, and be extra careful about anything and everything you do online.
As for getting another Samsung phone as an upgrade, Samsung does make some really good hardware, and some of the alterations it makes to the base Android operating system it installs on its products appeal to a lot of people, but there's also a lot of Samsung branding that adds a lot of bloat too. Buy another Samsung because you want to stay within Samsung's oversight, but I'd suggest you look into something like a Pixel phone for a clean Android device, or a OnePlus or Moto phone that will be have a minimum amount of added cruft and bloat. There are plenty of good, usable, reliable phones that aren't flagship models.
https://www.nytimes.com/wirecutter/reviews/best-budget-android-phone/