Essentially, this says all you need to know in one sentence or less:

Doorway Pages, on the other hand, are created by the type of person that thinks, “if I trick enough people into visiting this page, at least some of them will buy my crap.”

SOURCE: Landing page vs doorway pages

So yes, changing titles and a couple of keywords on the page would be considered doorway pages. Google's algorithm detects these types of pages and considers them both duplicate content and low quality. Users and Search engines hate these types of pages.

This type of behaviour is outdated SEO, nowadays Google and Bing will rewrite titles and even descriptions from keywords on the page, so even if the keyword is not in the title or description, these keywords can and do regularly occur in those positions when a user searches those terms.

Essentially, this says all you need to know in one sentence or less:

Doorway Pages, on the other hand, are created by the type of person that thinks, “if I trick enough people into visiting this page, at least some of them will buy my crap.”

SOURCE: Landing page vs doorway pages

So yes, changing titles and a couple of keywords on the page would be considered doorway pages. Google's algorithm detects these types of pages and considers them both duplicate content and low quality. Users and Search engines hate these types of pages.

This type of behaviour is outdated SEO, nowadays Google and Bing will rewrite titles and even descriptions from keywords on the page, so even if the keyword is not in the title or description, these keywords can and do regularly occur in those positions when a user searches those terms.