Nice question!
If a website is ranking for keywords related to my niche, I would definitely consider getting a guest post link from it.
A traffic drop alone is not a dealbreaker for me. Traffic naturally goes up and down, and I wouldn't reject a website just because its traffic has declined.
However, there are situations where I would avoid buying a guest post
-If the website has lost rankings across the board. If it has lost traffic for almost all its keywords, I would investigate further before spending money on it.
-If the website has become irrelevant to my niche. If it no longer ranks for relevant keywords and publishes content on random topics just to sell guest posts, I would avoid it.
-If the website's DR is high, but it has no real organic visibility. I wouldn't pay a premium just because a tool shows a high DR.
-If almost every article is sponsored content covering unrelated niches, that's a red flag for me.
For me, a traffic drop alone isn't enough to reject a website. I would look at what caused the drop, whether the website still has relevant search visibility, and whether the link is worth the price.
I wouldn't reject a site just because its traffic is dropping, but I wouldn't buy a link based on high DR alone either.
PS : Hope this helps many buyers here, as this is a common dilemma when buying guest posts from various sellers.