You're arguing for laziness, where there's more effort. The blanks don't just have to be a certain weight. They use a balanced metallurgy that is difficult to get right - especially as most peoples in that time and place had lost that particular level of skill.
If you reject abstract from Celtic culture, you reject the Celts. The Dagda isn't exactly some solid figure. They're an artistic people, in everything from their laws to... Their coins.
And as most family meals also intentionally left one part unfinished... For a deeply spiritual people, maybe you shouldn't be rejecting it out of hand.
As a small example, one of the most severe forms of punishment, was to ban an individual from religious rites, and another was to ban them from the construction of anything considered a 'craft' - something that would take skill.
Neither of those punishments banned the individual from the tuatha. They weren't exiled. They were still allowed to speak and be heard. They were still allowed to buy and sell. But they were no longer allowed to worship, or to create.
If you reject abstract from Celtic culture, you reject the Celts. The Dagda isn't exactly some solid figure. They're an artistic people, in everything from their laws to... Their coins.
And as most family meals also intentionally left one part unfinished... For a deeply spiritual people, maybe you shouldn't be rejecting it out of hand.