It is meant to procure electricity. That’s the entire point. The stated purpose of ITER+DEMO is to develop new power generation technologies!
The same argument can be made for any r&d, in lieu of spending on alternative technology that already exists. Should we have stopped spending on mRNA vaccines to pay for more socialized healthcare? Or more efficient batteries for better public transport?
No one knows the answer to any of these questions because the outcome of r&d is unknown. Some known unknowns but also unknown unknowns. So we do both/all the things to some degree and optimize the degree as we learn more. Alternatives are mostly not mutually exclusive.
Edit: formatting
Powering half of Europe for three decades sounds like a lot until you compare it to powering all of humanity for the next hundred thousand years.