Dealing with lead developer who hates functions [on hold]

I’m a new employee as Java backend developer in relatively succesful startup.

Startup has about 30 employees, mostly marketing / client relations, with only a few programmers, most of which are either junior level or working in other areas.

The lead developer dislikes writing functions and considers large blocks of code to be the best practice.

Most processes / services are written as one large function, often exceeding 500 lines of code.

Main argument being that there can only be utils and reusable functions. If a piece of code is not reusable then it must not exist as a separate function.

Thus there are no separate methods / classes for validations or assignments, since they’re always unique for the specific class and are mixed together with business logic.

I have to mention that the lead developer is actually a nice guy, very knowledgeable and friendly, so i’m extremely careful with choosing my wording, not trying to force my opinions or leave a bad impression.

Maybe i’m just losing my sanity and this is actually the best approach?