"Whatever a Russian does, they end up making the Kalashnikov gun"? Are there any similar proverbs in English?

I'm translating a Russian blog post into English and got stuck with the proverb, "Whatever a Russian does, they end up making the Kalashnikov gun." (Humorously meaning it's hard or even impossible to get past established patterns of doing things.)

Are there any similar proverbs in the English language?

I was trying to omit the reference to a particular nationality and think about other ways to get the message across, e.g. use professions or animals. The only idea I managed to come up with was "What can you expect from a hog but a grunt." But it has negative connotations that are not implied by the original.

I'd greatly appreciate if you share your thoughts on this. Thanks in advance!

P.S. Here's this bit that I'm translating:

A chunk of our budget was shelled out to buy game design documents prepared for us by two studios. The output was quite hefty. A great deal of work was done, no one's arguing. But what we got communicated a very different idea. Maybe even a good one, yet different. This proverb best describes the situation, “Whatever a Russian does, they end up making the Kalashnikov gun.” It was evident that people are used to and like doing things in a familiar way, based on their established practices for GDDs and without getting off the beaten track.

Source: habr.com/ru/company/uteam/blog/447310

If you are a hammer, everything looks like a nail.

The usual form of this saying is

If all you have is a hammer, everything looks like a nail,

but the above form is used, and might be closer to what you want.

Another famous aphorism is the following

you can't teach an old dog new tricks.

said to mean that it is very difficult to teach someone new skills or to change someone's habits or character (Cambridge Dictionary)

Usually said of people who set in their ways and are well past their twenties or thirties...