For 95% of users, this is a critical positive update . The performance gains significantly extend the usable life of the 2015-era hardware.
Firmware is the software that controls the TV's hardware components, such as the processor, memory, and input/output devices. It manages the TV's functionality, including picture and sound settings, network connectivity, and app support. Firmware updates are released periodically to fix bugs, improve performance, and add new features. Firmware Change Update on SONY KD-43X8309C
Never unplug the TV or turn off the power during the installation process, as this can cause the TV to become unresponsive and require professional repair. For 95% of users, this is a critical positive update