Google Analytics is all about web analytics, so you can see traffic sources, visitors, pageviews, custom events, conversion funnels, etc. Primarily your analysis is going to be around traffic sources and how individual pages are performing.

Product analytics tools are a little different in that they’re much more event based and allow for contact/account hierarchies. Ie you can group (and thus track) separate users under a single business entity. They’re also much more feature based, so you’ll primarily be looking at how features are used as opposed to app screens.

It's basically a spam engine. I had to stop using GA because Google, the billion dollar company with a million software engineers, couldn't figure out how to filter out spam from their product.

It's true.

Out of the box and just installed onto a site the data is garbage.

It provides more value to Google than it does the owner of a site.

Product analytics tool, is not the same as a web traffic analytics tool. Maybe that is what he meant.

Basically GA is more of a traffic measuring tool. It doesn't do perfect attribution of events and join them easily for you to build up a picture of the journey the customer takes.

Take for example something like Amplitude which lets you instrument and measure conversion or journey that a user takes across your product.