You’re definitely undervaluing the raw video encoding, transmission and delivery framework YouTube brings to bear there. Sure, you made a video. But that’s not the same as having a player that works in multiple browsers, support for multiple streaming bitrates and codecs, optimized global distribution and caching.. and that’s all before we get to the discoverability, hosting and channel management features.
But with a video you have the portability to take your content somewhere other than Youtube for the supporting infrastructure. Your Roblox game is much less portable.