That's the least of the problems.

At some point Google Groups got really inconsistent, where it didn't turn up many, many postings and threads when searching for them. For some time you could find them if you tried several of their country TLDs (google.de, google.com), they brought up different results.

A bit later even that didn't work anymore, Google Groups has spotty coverage, at best.

Then they hid their advanced search interface. If you knew the URL you could still use it. Then they removed it altogether.

Nowadays you have probably no way to specifically search for something ("author:", "group:", "mid:"), nothing is working satisfactorily anymore).