So you hold separately the ideal of social democracy in your head from its actual implementation you see in the real world. Maybe you should consider how the fundamentals of social democracy might just naturally lead to the problems you see with the current social democratic party.

A lot of communists online do the same thing you're doing; not reconciling the ideal they have in their head with the actual implementation in reality. Just like how there are fundamental problems with Marxist theory that result in attempts to implement it devolving into authoritarianism (centralised state power, vangaurdism, "dictatorship of the proletariat", cults of personality, etc.), there are fundamental problems with social democracy that result in flaws in its implementation (weak/shallow analysis of power dynamics, reliance on imperialism/colonialism in the form of unequal exchange, regulatory capture, influence of money in politics, etc.)

Generally, as long as the economic system allows wealth to be converted to political power (as in the case of social democracy), or the political system allows political power to be converted to wealth (as in the case of centralized state communism), there will be corruption that eventually snowballs into major issues that cannot be solved by working within the same system.