Everyone is too old for a sequel to the original.
And much of today's audience wasn't even born when the original came out, over two decades ago. And, as much as it's fondly remembered in certain circles, the first movie failed at the box office. So this really isn't a case of "if it's not broke . . . ." It broke the first time out, twenty-plus years ago.
So, yeah, Disney can be forgiven for not wanting to do a sequel to a flop from over twenty years ago!
Starting over is the only sensible plan.