According to scientists who have devoted their lives to studying this field, who know far more about it than you or me, the Holocene extinction is classified as one of the 6 major mass extinction events.
The Quaternary extinction (form 130,000 to 8,000 BCE, part of which was the Younger Dryas extinction -
link) is not.
Therefore, the position that the Younger Dryas extinction (which was only part of the
Quaternary extinction) is greater or more significant than the Holocene extinction, is clearly false according to current evidence.
And I don't even want to get into the discussion that the reason for the Quaternary (and the Younger Dryas) extinctions is unclear (the
wiki page describes the arguments for/against the various hypotheses - including the climate change hypothesis, which you present as fact - and states that
"recent studies have tended to favor the human-overkill theory").
Arguing that the reason we think the Holocene extinction is greater (or cause by humans) is that
"we know way more about it for obvious reasons" is a prime example motivated reasoning. For one, you are disagreeing with the scientists who know infinitely more about the field than you do. And for another, if there isn't enough evidence, then how can you argue that your position is anything more than a hypothesis that is unsupported by existing evidence?