Terry Wogan went exactly the same way as Jimmy Young by the end - he developed a mannered and prissy way of speaking that was unlike anyone else talking anywhere, ever! He either leaned into the mic and dropped his voice to the 'soothing blarney', or he ROARED LIKE A FORCE RIGHT GALE sometimes doing both in the same sentence. His delivery had become ripe for charicaturists, the sure sign it's time to go - which he has.
Objectively, the BBC cannot find another Wogan - even if they should wish to - so they haven't tried. Evans is a skillful broadcaster and he will loose a core of Wogan fans and gain some more new radio listeners who disliked Wogan's style.
Twas ever thus - nothing is forever, it's a radio show not a listed building - let's move on and let the past go.