The SF Giants' offense has been terrible for a while now with no end in sight
The hardest part of contending with a roster like the Giants' is stringing together consistent offense. A pitching staff can be managed and can target specific matchups to find success, but when a lineup lacks blue chip players, essentially everyone has to play reasonably well to make it work. It certainly isn't impossible to pull off, but not having a guy or two that can carry the offensive load means that everyone has to do their part.
Unfortunately for the Giants, that hasn't been the case for a while now. Since August 1st, the Giants offense has ranked 23rd in all of baseball by fWAR at 2.7. and 24th in wRC+ at 91. Those aren't just subpar numbers, they are downright bad. If you are looking for good news, it is that all of the NL teams contending for that last wild card spot seem to be in the same boat as the Reds, Diamondbacks, and Marlins offenses have all struggled lately.
Aside from the lineup just not playing well, the Giants have dealt with their fair share of injuries. Thairo Estrada was on the shelf for a while and he has not been anywhere close to the same player he was in the first half since returning. San Francisco also has two of their better bats hurt right now in Michael Conforto (hamstring) and Patrick Bailey (concussion).
Both Bailey and Conforto SHOULD be able to return soon at the very least. If those two guys come back and hit like they are supposed to, the Giants have a chance. If not, it could be a painful end to San Francisco's season.