They did age, though...Moreover, the style of the animals (the hen and chicken is the prime example) is in the fashion of the thirties.
Latter point, yes, I agree, which is why I agreed with the 1990s decision (never carried out) to adopt the hound and the hare but NOT the hen and chicks. However, all designs age: sometimes after only 10 years, but usually after 15 years their vintage is apparent. But is that a good reason to drop them, if they are nonetheless still popular, as the Metcalfe designs were in Ireland? Switzerland's designs date from the 1860s, I understand. I remember complaining about the return of hoary old Britannia to the UK coinage, on the 2 pound coin, and was astonished to find the forum's token "social justice warrior" disagreeing with me.

Popularity isn't everything, of course, but the Metcalfe designs most certainly are popular, not just in Ireland but around the world. And that is why, as I pointed out, his designs have been adapted for collector coins but those of Miss Hayes have not.
The question is rather if the Celtic designs were more representative of the modern Ireland. As far as subject is concerned, clearly not. However, in spirit, they do represent the Celtic essence of the country.
I would beware of speaking of the essence of a country. (I'm thinking of my evolving series of topics on fascism). All nations are composed of different facets.
In addition, their abstract quality makes them timeless
I'd disagree. They always looked distinctly medieval to me. Nor did they age well, as I saw circulated pieces on the Isle of Man in the 1970s, and they looked dreckid, whereas the circulated pre-decimal bronze pieces still look very attractive. However, designs rarely look timeless, as that is probably impossible, nor is there any requirement that they should, of course.
That leaves the "unity of series" argument. I think it is carried too far in the discussion as reflected above. For a considerable time, all UK copper had a seated Britannia, while the rest of the series was heraldics only.
Yes, for a while the series was a distinct mish-mash, as it included the wren farthing and the ship ha'penny, amid the symbolic and the heraldic.
That is not the only example. There are quite a few series that have designs in a different style for the coppers.
It's true, but whether it is a good idea is another matter. Some design series, such as the Austrian pre-euro series, were a total mess.
I have sympathy for the changeover argument, so I understand a design that signals "a shilling is 5 pence". However, logically that means that the style can also signal "a penny is not 1 pence".

Apart from anything else, that is also ungrammatical.
"Just gotta warn ya,
Give you the strap,
Stand you in the corner,
Dunce's cap!"

Therefore, the designs I would have chosen differently is that of the 20p and the pound. While they would not necessarily have had more Celtic birds, they could have been decorated with other Celtic designs and their introduction could have been used to do the same thing with the 5, 10 and 50.
While for various reasons I do not think the 20p was a success, I regard the Irish pound as a classic. The stag is a superb design.

It took the Metcalfe template and improved on it, making it modern and relevant. Shame on you, for not seeing that! And Celticise EVERYTHING?

OK, uniformity is better than a lack of it, but I would have modernised in the Metcalfe style, since that would have been more democratic, as in "what most Irish would have wanted", given the continuing popularity of the Metcalfe designs.
After all, it was no longer necessary to specify "new pennies" either.
Mr Figleaf, please! You really haven't done your homework. Unlike the UK coinage, the Irish coins never did include the word "new", only the denominational numerals alongside a "p".
In sum, I charge you with the heinous crime of having all the wrong opinions. I hereby suspend you for a fortnight and sentence you to pay half the Brexit withdrawal fee. You are also ordered to pay a 15 euro note to every Irishman, wherever he may live (but not to every Irishwoman, for fear she might donate it to the Catholic church). Finally, you are required to attend my master class in coin design:
Circulation sets with poorly unified design.
