Absolutely not true. Series get completed. ASOIAF was NEVER sold as a "may never be finished, read at your own risk" experience or some sort of episodic series like The Dresden Files. It was ALWAYS billed as a story GRRM knew, from start to finish, first as 3-4 books, then 5, now 7. He ALWAYS talked like the later books were mostly done, hell he was doing chapter releases YEARS and YEARS ago. So readers jump on board with the DEFINITE expectation that, barring GRRMs untimely death (now not so untimely), this series would get done and his initial pace would have had it all out in 10, maybe 15 years TOTAL, not the 30 year odyssey we are on now. The way this series has fallen into the shitter is 100% an issue with GRRM taking the audience for a ride. This was not some series from some reclusive author where it may or may no ever finish. GRRM was prolific, timely, and productive in the 80's/90's through mid '00's, at which point he fell into the abyss.
It is when he was, and still is at some point, putting out "I'm working on it, almost there!" posts. It's as obvious a "rope a dope" scheme as can be at this point. Am I gonna sue him for a full return of all the money I've spent on ASOIAF books? Of course not. But was my investment into the series predicated on his OWN ADVERTIZEMENT that the series had a definite conclusion, just a few books away. 10000000000000000000000000000000000000000%
If the show is all the resolution we get, with all the hanging chads in the form of Lady Stoneheart, that young Griff guy, etc, then the series would be a major failure from my perspective, at least past the first 3 books as sort of a sad tale of the Fall of the Starks.