All fusioned champs in 2020 are trash, including Rotos who was nerfed in mid 2020.

If P necro old fusions, 80% players will never do it again. 

They said going forward almost all fusions will be new champs. They threw that almost in to try and prevent people from feeling like they wasted time and energy storing champs and to make you not use all your stored champs as food. I would reccomend that you just use them as food though, that's what I'm doing. The odds of them being used for fusions are slim to none because then plarium couldn't make as much money off of people who need to earn the champs during the event. 

Just keep one. We may never know if that "trash" will get buff or become usable in future content in the game.