> I am, of course, in no position to question senior dev

Don't assume senior devs know necessarily better. There's a wide range of abilities in our profession!

That being said software engineering is made of trade offs and your colleagues may be aware of the issues you mention. Maybe this was decided on purpose based on constraints at the time, or maybe it was a bad design, but it's now costly to fix.

In any case, you should probably not question them and re-assess the case when you have more experience and seniority in the company.

It's still very important to know the best practices, but it doesn't mean they have to be followed blindly in all situations.