Reina was never "awful". David James from 1996 onwards was awful, and Dudek in his last two seasons was awful.
Pepe's Liverpool career simply went stale. Both the player and the club needed a new beginning. I think he can be a world class goalkeeper again, but I don't think it was going to happen with us, so it was the right decision. In the last 2 seasons, there was 6-10 goals where Reina was either directly at fault for, or should have done better. Home and away against City, he cost us points last season.
And in Mignolet, we've signed a superb goalkeeping talent who will only get better.