Code quality is very real, but the bounds you have to exceed before lack of quality start to bog down development are pretty large.
As a senior I can pretty quickly tell in the languages I write in often, when something is a smell, and if you keep repeating some code smells for a like a year you'll start seeing compounding effects on development speed. Understanding when to allow those with good reason and when to coach someone to stop doing those is an important skill for a senior imo.
But it's definitely not immediate, way more of a pernicious concern, the codebase will effectively rot until it's painful to make changes.
Eh, I've seen a number of startups sunk (as in went-out-of-business sunk) because of code quality issues. Eventually you hit a wall where every bug you fix introduces more bugs, and the product does not converge to a state where you can launch it. Then the VCs start getting impatient and you run out of money.
The point where this happens depends a lot on problem domain. If you're doing well-understood CRUD-screen database stuff but applying it to a novel business domain, you're probably not going to hit code quality issues. If you're doing heavy algorithmic, OS, financial, or networking stuff, though, where failures compound and any one bug might take the whole system down, you really want to pay up for experienced developers that have seen all the ways these systems can fail.
Oh sure, I didn't mean to suggest code quality can't kill a business. I however think like you said it's very domain dependent on how quickly that happens. I think taking on no debt wrt to code quality is impossible though and knowing how to take on that debt and pay it down to effectively meet the broader business goals without doing irreparable harm is something everyone has to contend with while being a dev.
That said, I can really only speak to web api dev, data engineering and search. I'd say out of all of those search was the tightest area with regards to quality and even then I was lucky to be working with another very talented dev. Him and I didn't run into very many issues we were unable to solve with scaling the technology even after hitting 100m pages or so and we could have kept going on scale but we were cost constrained, navigating the business side was far more challenging for us.
I'll admit as well I've been pretty lucky so far to work in situations where code quality is considered and managed and haven't yet worked somewhere where the concerns were entirely ignored or the team didn't care.
As a senior I can pretty quickly tell in the languages I write in often, when something is a smell, and if you keep repeating some code smells for a like a year you'll start seeing compounding effects on development speed. Understanding when to allow those with good reason and when to coach someone to stop doing those is an important skill for a senior imo.
But it's definitely not immediate, way more of a pernicious concern, the codebase will effectively rot until it's painful to make changes.