Yes, the YEC position is impossible to defend. And the "old hands", the creationists who have sallied forth and gotten creamed, know that even if they can't admit it to themselves. That is why they avoid having to defend it by controlling all their venues. Debates are nearly perfect, because the creationist can freely lie about everything and anything while their opponent feels constrained to being truthful -- eg, in Bill Morgan's debate with Phil Summerfeld (on YouTube), Morgan quoted a PhD Molecular Genetics, making sure to over-emphasize her PhD, without ever mentioning that she's a professional creationist speaking as a creationist. Presentations also, though in an article about creationist debates I read about a presentation where the creationists learned that a couple guys familiar with creationist claims were in the audience so they had to quickly change their presentation.
The bottom line is that, even though YEC is impossible to defend, they persist in believing in it. That's why they're called
PRATTs. It's like on Doctor Who: No matter how many times you kill or annihilate ( the Daleks / the Cybermen / Devros / the Master / YEC claims ), they keep coming back in subsequent episodes.
They refuse to stay dead!
The only thing that would result in a decreased number of YECs would be a decreased number of fundamentalists (to apply a single term to a number of different Christian YEC cults). The main thing lowering their numbers is the hemorrhaging of their youth, the next generation which they had raised themselves. The estimates of how many fundamentalist Christian youth leave the faith (with many of them leaving religion altogether) range from 65% to 80% -- interestingly, as I recall, the higher figures come from sources in the youth ministries. As a result, the only way those churches can maintain their membership numbers is through more aggressive recruiting, AKA proselytizing, for which they rely heavily on the "creation science" position which is so impossible to defend.
YEC is not about to go away. But the experienced YECs know all too well to avoid EvC. And the nave newbies are now being drawn to other forms of communication, to social media, which is better suited to YEC's superficial hit-and-run tactics and avoidance of any actual discussion of their claims.