Subdomains on the service website through shortcodes, is it dangerous?

Question

Search Engine Optimization

Auto-services website (about 200 pages service + brand + model), the other day familiar programmers suggested making a choice of million-plus cities on the site. Implementation through aliases and shortcodes, as far as I know what it's called (cities, addresses, phone numbers). But a familiar SEO specialist began to convince that it was so dangerous and that one could fall under the filters. So far, this method has shown itself well for 2 months, and the pages are perfectly indexed in those cities where they were not there before, sometimes the positions are already higher than on the main site. Plus, there are 2 competitors in the top 3 in the search - leaders in the niche, for almost all queries, they also implement shortcodes (page content, texts, photos are the same, only the city name and phone number change).
I heard that Yandex loves such sites and they quickly climb to the top by region, but Google, on the contrary, has unique content with real subfolders, or new sites or subsites are generally better.

Question : What is your experience with this?

Answer 1

That's right, Google is against monopolization, and by creating the same sites with slight differences on subdomains, you thereby put yourself at risk of getting a filter on all sites, since it turns out that you are trying to capture the market, and with low-quality content (since it is duplicated, judging by your description).
Sites will not immediately fall under the filter, the time will come and at one fine moment they will be thrown out of the TOP and trust will not be returned (or it will be very difficult to get out, it will take a lot of time).