iPads are not a full gaming machine, IMSO.
And Apple states UP to 9-10 hours and it actually lists what they did with an iPad to get to that battery life
Quote from Apple.
“All models
Up to 10 hours of surfing the web on Wi-Fi or watching video
Wi-Fi + Cellular models
Up to 9 hours of surfing the web using cellular data network”
“Testing conducted by Apple in February 2020 using preproduction iPad Pro 11‑inch (2nd generation) and iPad Pro 12.9‑inch (4th generation) units and software. Testing consisted of full battery discharge while performing each of the following tasks: video playback and internet browsing using Wi‑Fi or cellular data network. Video content was a repeated 2-hour 23-minute movie purchased from the iTunes Store. Internet over Wi‑Fi and cellular data network tests were conducted using dedicated web servers, browsing snapshot versions of 20 popular web pages. All settings were default except: Wi‑Fi was associated with a network (except for internet browsing over cellular data network); the Wi‑Fi feature Ask to Join Networks and Auto-Brightness were turned off; Brightness was set to 50%; and WPA2 encryption was enabled. Battery life depends on device settings, usage, and many other factors. Battery tests are conducted using specific iPad units; actual results may vary”
You might get longer battery life to start by NOT using full screen brightness and experiment with different screen brightness setting until you find an optimal screen brightness setting.
Screen brightness IS THE NUMBER ONE BATTERY POWER DEPLETER!
Best of Luck to You!