This has to do with all the services running in the background. Modern phones are actually extremely efficient, providing you're not connected to push notification services and don't have apps running in the background all the time.
Problem is that Google and Apple loooove user data and so it's very hard to do this, impossible in the case of iOS. I have a fully google-less tablet and that things lasts many days on 1 charge.
Also scrolling on TikTok is basically the most intensive thing you can do on your phone unless you play 3d games. Lots of data being transferred, lots of effects, you KNOW it's sucking as much data as it can out of your phone too.
What OS are you running on your tablet? I am running Graphene on my phone, and the battery isn't bad, but I bought a Pixel specifically for the purpose and don't have a baseline to compare it to.
Shitty Samsung Tab A8, it's a random XDA developers AOSP ROM that I've removed Google garbage from. I don't like the Samsung skin, it's slow and has a ton of bloatware. Because I don't need push notifs on it, there are no gapps replacements installed on it either. So I just use all F-Droid apps since I just browse the internet, read books, and read manga with it. Newpipe for YouTube.
My Graphene P7 gets worse battery because I do need some services running for push notifs and such.