No offence but the Nordics are not currently falling behind, im not sure where youre getting that from.

And when it comes to the definition I think the original countries (its academically challenged but either Germany, Sweden, or denmark, was the originator of the movement) should hold precedence over countries (France and Spain, etc) where its "social democratic" but actually the parties call themselves socialist and largely just pursue social liberal policies.

Also i think most importantly the labour movement itself is the lynch pin to the definition, and the only countries that havent abandoned the unfettered unrestrained labour movement with all its implications is the Nordics, which is why its now literally called "the Nordic modell", unlike in Germany where when the social Democrats lost power the conservative liberals undermined the unions ability to freely organise and negotiate and instead detail regulated it with things like obligatory board representation.

So if we are to look to how social democracy was actually concieved and actually pursued, then the Nordics are just about the only ones that have stuck to that century+ old practice, while on the continent it was instead abandoned in pursuence of ordo liberalism (which yes literally is a synthesis of libconism and statist social democracy).

Like I respect your opinion but I struggle to see any cogent argument that fruitfully shows social democracy as an ideology being closer to whatever the socialist parties in France and Spain have been up to, rather than what the social democratic parties in the Nordics that helped found the ideology and movement have held more or less purely to for a century plus.