(I'm Not OP) - At the end of the day we're all trying to strike a balance between shipping fast and keeping technical debt down. Asking juniors to only ship code that's good as what a senior would write is very rarely the right balance point. Senior engineers must learn to understand when code is "good enough". If you're a senior and you haven't developed this skill you're bringing your team down.

Concretely, a heuristic I rely on is to understand whether the sub-par code being added "infects" the code base e.g. it changes an important interface, it adds a poorly designed interface other code will rely on etc. These are the places its important to put your foot down. Conversely, if the internals of a one-off function or class could be a little cleaner... eh, ship it.