The Gunners fell behind inside a minute when Martin Skrtel tapped home from six yards, before the defender guided a header in for his second shortly after.
Liverpool were pouring forward at every opportunity and Raheem Sterling tapped in before Daniel Sturridge added a fourth before half-time at Anfield.
Sterling then netted the fifth from close range in the 52nd minute, before Mikel Arteta dispatched his penalty after Steven Gerrard had brought down Alex Oxlade-Chamberlain.
It raises some questions today because we were caught many times and were a bit naive
The defeat left Arsenal top of the table but both Manchester City and Chelsea can move above the Gunners if they win their games on Saturday.
“I felt that it was a very poor day,” Wenger, whose side host Manchester City on Wednesday, told BT Sport. “Only our fans were good for 90 minutes. We were poor defensively and offensively and we were always caught in slow-motion.
“On top of that, we were caught on two set-pieces at the start but the performance was very poor and Liverpool played very well, so congratulations to them. We have to bounce back as quickly as possible.
“[We must show] the desire to give the right response. These are top-level sportsmen who have shown since the start of the season that we can do that. But of course it raises some questions today because we were caught many times and were a bit naive.
“I’m confident we will bounce back but of course we produced a poor performance on a day when we couldn’t afford it. We have to think why it happened and make sure that it doesn’t happen again.
“Certainly we need to be defensively more stable because today we were too open. Every acceleration from Liverpool was deadly for us. From up front to the back, we were not at the level that we are used to.”
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news