It’d be hard to imagine that Loki would have been popular had the MCU entries of the late 2000s-early 2010s (where he was from) been production-wise similar to the MCU entries of today. Like everything in Ragnarok, Loki was very funny there but his story and character depth was lacking. And while I found the second season of Loki to be an improvement; it still wasn’t really a show about him and moreso setting up Kang and the multiverse.
They’d have to dedicate a decent amount of time developing Doom’s character for it to work and I unclear on it happening with everything needing to be on time so to speak. Not to mention a good actor