New villains are necessary to produce new stories, but I also wish Marvel would dig a little deeper and revitalize existing villains (Astra, Empath, John Sublime, Azazel, Dark Beast, Madelyne Pryor etc.)
It's frustrating that writers hit reset with characters that have an antagonistic past, even when other writers try to evolve them beyond that. Magneto, Mystique, Sabretooth, Daken, Juggernaut, Spiral, Emma Frost... the list goes on. They're more interesting when they have a motivation beyond wanting to rule, or the satisfaction they find in murdering and manipulating their way through life. One of the big reasons I'm frustrated with Mystique being on Creeds crew is that Bunn & Soule made a point of giving Raven clarity, and 'taming' her mind, which previously changed each time she shifted her form. I'd hoped that she would find some direction in her life, and do something more meaningful than being on a kill crew