Definitely not. It's basically 99% trash 1% good. Like you'll find good episodes here and there but there's way too much junk to wade through.
The only two stand-out episodes, IMO, are S6E15 and S10E05. First one is basically what happens if Dean and Sam enter the real world, funny stuff. While the other is a fun musical that retreads bits of S1-5.
Going to have to completely disagree here. I'm nearing the end of my complete series rewatch (on season 10) and despite the up and down nature of quality, saying it's 99% trash is pure hyperbole.
Season 6 is a very mixed bag but I mean, you're forgetting "The Man Who Would Be King," which is a fantastic episode that showed how Cas ended up where he was. Dean as Death for a day and the wild west episodes were good. The fairy episode was very funny.
Season 7 is a mess, no doubt. Arguably the worst season of the show. It starts out very strong and Mark Pellegrino was amazing in Sam's visions but it's clear they had no idea what they were doing with the Leviathan arc and they badly misplayed the "ghost Bobby" idea. "Death's Door" is one of the best episodes of the series, however, and certainly belongs up there with the two you mentioned.
Season 8 is really good and a return to form. Crowley was a great Big Bad, closing the gates of Hell/the Trials was an interesting idea, introducing the bunker and the Men of Letters was awesome, Benny and Kevin were really good characters. The second half is definitely better thanks to no Sam/Amelia flashbacks and it had arguably the best finale in the series other than season 5.
Season 9 was fairly weak overall as it squandered the potential from the angels falling and Cas becoming human. This was really the peak of the Dean/Sam fighting angst and it was way too much at times. But it also had "First Born," "Meta Fiction," and "Blade Runners."
I remember season 10 being somewhat solid after botching the Demon Dean idea in the beginning but I just got to that in my rewatch so I won't give a full opinion yet.
But season 11 is just awesome. Easily one of the best seasons with a lot of great mythology episodes and some of the best standalone episodes in years.
It's definitely worth watching Supernatural after season 5. Even during its low points, it remains entertaining due to the characters. But it still has plenty of moments of greatness and seasons 8 and 11 are legitimately great -- especially 11. The only season I would label as truly bad is season 7.