Sure, but the video vulnerability is just the quickest RCE vuln I could find for the Galaxy Note 5. I'll bet if I go back to the Android CVE database I could find more vulnerabilities of various kinds that the Note 5 is susceptible to, and that we'll uncover more in the future. And looking at Stagefright, the way you use your phone is no guarantee that you can dodge vulnerabilities.
It's up to you whether you are comfortable with the risk of running as unpatched phone. But a risk is very much present, and only using a couple of apps doesn't protect you from getting hacked and keylogged at the very least.
There's not much I do outside the Chrome browser—no social media apps. I can count my downloaded apps on two hands.