It was designed to accomplish all of its primary goals on battery power alone, which is a big factor in why they didn't want to complicate the mission with something like an RTG, while solar cells are simpler to add on in the hopes of getting an extended mission. Of the 10 instruments on board, 9 worked and collected useful data, with the drill being the one exception. Several of the instruments were of limited repeated use or would be unable to be powered under solar power even in ideal conditions. The only long term instruments would have been basically plasma monitoring equipment.
That's what people don't get. The lander was basically designed as if it wouldn't have reliable solar power. If it did, then there was an extended mission where it could continue to collect additional data. Really, the biggest failure was the landing system which was supposed to anchor it down. If that had worked, it wouldn't have bounced all over the place and it likely would have had enough light for the solar panels to work. It's also likely that they would have been able to use the drill. But even with the way it ended up, it was still able to perform most of it's primary mission.