The original Deck was a horrible device for Moonlight.
You had Logitech G Cloud with a nicer quality screen and better battery life
You had phones and tablets that can stream at higher frame rates
You had hacked Switch OLED and phones and tablets that had a nicer OLED screen for streaming
You had phoned and tablets as well as Odin Lite that had WiFi 6
But now with Deck OLED you have a nicer OLED screen that supports HDR. You can stream at 90fps. You have a better WiFi 6 chip. And the device is slightly lighter with better battery life. You can also use the touchpads. The only other devices that rivals Deck OLED is Rog Ally with its 1080p VRR 120fps screen or the Legion Go with its 1600p 144fps screen.
Nothing sucks about streaming to the original Deck. Full controller with analog triggers (unlike Switch), and touchpads (unlike most other options.) Battery is pretty great if you’re just streaming the game. Nothing wrong with it in my opinion.