I think you're basically proving my point? (My point being: politics isn't just "getting elected".)

In such political systems where you essentially must vote the party line, what makes an individual "effective" (ie. what constitutes being "good" at your role)? I'd say it comes down to all kinds of political soft skills, ie. forging the right alliances, convincing the right people to change course, understanding motivations of others, etc.

All of these are generally called "politics", and are things that happen very much after you're elected.