I want to burn it to a blank DVD.
QuickTime Player is not a DVD-Video authoring software. It is a media player, that can also do some basic recording (camera/mic to file).
Your Mac doesn’t come bundled with DVD-Video authoring software (anymore). You would need to use third party software, if you want this disc to be playable on a standards-compliant set-top DVD player connected to a TV. I can attest for both the softwares mentioned by Jeffrey; they work well.
Burning a regular file to DVD-R without authoring would be readable on computers only, depending on the chosen file system (ISO 9660 or UDF for compatibility, or HFS+ for Macs only).
There is virtually no need to burn discs anymore in 2024. Many TVs can play .mp4 files without authoring, directly from USB stick, or through a HDMI connection, or through AirPlay streaming. The only reason to burn a disc is legacy use by acquaintances that refuse to get with the times. It’s possible, but DVD-Video is also SD low resolution (480p NTSC/576p PAL), while HD or more is attainable by not doing DVD-Video.