Unfortunately the greens* have done a good job of making nuclear a lot more expensive, and produce a lot more "waste", than it needs to be.
For example, decommissioning of the old Magnox reactors was actually considered, and a plan was in place. Plan
iswas simple - turn it off and keep cooling it for a while, remove the fuel and remove all the ancillary stuff leaving you with the primary containment about the size of a house. Post some guards in case someone wants to graffiti it or something, and leave it to cool down for (say) 100 years. As anyone who actually understands "things nucular", something is either long lived OR it's highly active - it cannot be highly active and long lived. After 100 years the radioactivity level is low enough, so I've been told by someone who knows about this stuff, that you can cut a hole in the side, walk in, and carry out the carbon blocks making up the moderator.
But no, the greens* insist that we can't do the sensible thing, we have to do it the most expensive way possible - meaning to dismantle a "hot" reactor and find something to do with all the highly active stuff while it cools down.
Similarly, a lot of the "waste" that we are being forced to get rid of at great expense could (as you point out) be considered fuel in the right type of reactor - vastly reducing the quantity of waste to be dealt with. But again, for political reasons this isn't happening - not for valid technical or economic reasons, but the green* PR machine can't allow plutonium to exist even if it's then fuel for a reactor.
AIUI there is enough
wastefuel already in storage in the UK for us to be 100% nuclear for at least a century if we had the right reactor fleet.
* Certain factions. No matter what you want to do, you will find someone in the "green" movement who is against it for some "green" reason.