Unfortunately google is the only way to search old usenet archives from the web, since they bought out such archives. That search leaves much to be desired.

Only the relevance search has results for usenet posts, you can't order by date, and other then using date ranges, there's no way to only see usenet posts.

For example searching for "gamer" before 1/1/2000:

relevance https://groups.google.com/forum/#!search/%22gamer%22$20befor...

date https://groups.google.com/forum/#!search/%22gamer%22$20befor...