iPad battery replacement or new iPad?

That's a choice only you can make. Personally, given iPad 5 was released in 2017, 5 years ago, I would be more inclined to trade in the device and move up to a newer model iPad. Your iPad is getting closer to end of support, though we as users have no information when that will actually happen.

Hello The_Lily,

You can find some good information about your iPad battery here: About the battery usage on your iPhone, iPad, and iPod touch

Please check out the "Learn more" section of the above link for some information on how to determine if the battery needs to be replaced.

For more information on iPad battery service, please check out this link: iPad Service and Repair

If you have additional questions, please contact Apple Support. You may be able to reach them here: Get Support

Take care!