Season 4 is where it started to fall apart. Season 6 through 8 suffered terribly with the shift in writing and structure, and I'd be happy to never watch any of those episodes again.
But I agree with Lost. "Really original show but it pretty much goes off the rails."
To everyone's surprise, there isn't any payoff, and there aren't any consequences.
It was not really a surprise. As you said things went off the rails for a while already, that was a sign of a bad ending early on. When I saw how quickly they wrapped the Night King in Season 8 I knew all hopes were lost for a good ending.
That's a pretty lame sales pitch. I think you meant you wouldn't mind recommending them, but then you wrote out a quote as if it were actually a pitch
The "pitch" for catching up on GOT now is much weaker now than it was midway through the series.
An awesome show becoming an ok show and then ending as a terrible show is not worth recommending for anyone.
For me Lost, was a great show, with highs and lows, with fairly good last season, with a very disappointing and confusing last episode. Still worth the ride in my opinion.
If you feel characterization is the most important thing, and the emotional connection to characters or having highly evocative emotional moments in the narrative is what makes it worthwhile then you will probably like Lost quite a bit, but you might hate GoT (given my understanding that the last season fucked up major characters for shock value - I can't speak directly to it as I haven't watched it)
So based on that my wife still talks about how great Lost was, and if it gets brought up the first words out of my mouth will not be complimentary.
I'm not sure I would recommend your examples to a friend though. GOT started going downhill around season 5; it wasn't just the ending that was bad. I'm sure people would disagree with me here, but I think lost hasn't aged very well. it was a good show only by the mediocre standards of '00s TV.