from google's point of view there's no maximum. The more walls of text you feed the retarded googlebot the happier it will be... if bots can even be happy (and I'm afraid of finding out the answer...)
But you have to think from the perspective of the user: would someone read 8k words long walls of text? My guess is that only in certain niches like SEO probably... or programming / coding when there's a lot of code to showcase... or maybe if you want to teach someone how to macrame in one go, that might work, too. But for most niches and keywords writing 8k words articles is boring as fuck to read, even I hate reading that much content nowadays and I used to be an advocate of blogging over vlogging...
Anyway, the point is that google will not penalize you directly for writing so much content, but if your users get bored and click BACK fast, without interacting with your page in any way, google will see this and might penalize your content indirectly for having low performance / engagement. So, in the end it will still bite you in the ass....
Just write enough words to properly address the intent of the keyword you are targeting and if it turns out to be 2k words long content, be it! But most of the time you should stick to 800-1500 words long articles, I think that's the sweet spot...
