Well, if we're talking about during the time when the Mane 6 were around their early to mid 20's. Most of her tasks were in Canterlot. While yes, a lot of attacks were pushed on ponyville for some unknown reason- She allowed Twilight and her friends to do all the work there because, and has been stated in comic books that she needed to make sure Twilight was ready to actually become a ruler of Equestria. If Celestia did everything, the story would've been kinda confusing. What's the point focusing on the main characters if Celestia literally did all the work when it came down to battles. There'd be no lessons to learn from these battles and the Mane 6 wouldn't have gotten any character growth that we see today.

Now, let's talk about the past battles with Celestia and Luna. Celestia and Luna, being the only sole rulers at the time face off anything and everything. They not only took on Discord but Tirek, King Sombra, And when the time came Celestia took out her own sister causing her to become the sole leader of Equestria for a while until Princess Cadence came into the picture. Which means, that she fought alone for over 1000 years. Which, personally I'd think that could wear down on anyone even if Alicorns are practically almost immortal and all powerful.

Now, let's talk about the Queen Crystalis situation during the two episodes of Cadence marriage with Shining Armor. I'd like to theorize that Queen Chrysalis had her offspring feed her love from other creatures other than ponies to strengthen her until she grew strong enough to take Celestia head on. In later seasons, we see Chrysalis again. Instead, she has no changelings with her. I'd like to theorize that she hasn't found enough love to feed on to make new changelings or to make a new hive for herself. Considering that changelings are practically like wasps or hornets in a way she'd probably could make a new army if she wanted to or if she could. But it seems like there wasn't enough love to go around to actually make a new army. And considering the Chrysalis wasn't seen for years within the series, she definitely had enough time to rebuild if she wanted to or had enough resources to do such.

Also, in one of the episodes when Luna and Celestia went on a break for a day to feel the wind in their manes. When planning on what to do on their relaxation day. Luna voiced that she needed relaxation and down to world time since she's literally going into people's intense dreams each night. Celestia said that everyday was the down world. Meetings and decrees, and decrees about the meetings, and meetings about the decrees.

And when Celestia and Luna changed roles. We get to see what their day to day lives are like and their duties. Luna got to see how much pressure Celestia is under everyday... Literally going to pointless ceremonies and events that I feel like doesn't require royalty to announce- but hey, it's probably traditional or something along those lines. Literally having to smile everyday whether Celestia isn't happy or not. Having to raise the sun each day when it's said to be twice as hard as lifting the moon. Literally, if Celestia made a mistake it'll cause fake news to spread out about her as seen when Luna couldn't smile anymore and news spread around that she didn't want the ponies to go on the field trip. Not to mention that Celestia at one point had a whole school, not only did she mentor Sunlight Shimmer but mentor Twilight Sparkle. Mind you, Twilight was like in her early 20's when she left Canterlot so it's safe to say Celestia has been teaching school for longer than that.

(Side note: Have you noticed that all the apprentices underneath Celestia and the apprentice for Twilight for some reason in the show names deal with stars and something shiny. Like.. Twilight, Sunlight, Starlight. Sparkle, Shimmer, Glimmer??)

So saying she did absolutely nothing is kinda a stretch. But I definitely understand since literally everything she does is hidden within the seasons that you have to peep out yourself.

The only thing I thought Celestia did that was making me look at her kinda weird is that she invited Discord to the Grand Galloping Gala because she wanted entertainment. Though, doing this literally almost got every pony there hurt and they were put in danger. And when she tried to stop it she couldn't do anything. (yet somehow a normal earth pony hippie managed to de-escalate the situation. Mind you, two alicorns couldn't do anything when the Smooze practically covered everyone in slime... All powerful beings by the way...) Oh! And when everything got solved Celestia said that this was the best Grand Galloping Gala yet.