Current status of deprecated tags:

abstract-algebra 355 questions; if we only count questions which do not have another algebra-related tag, then it is 210 questions. mathoverflow.net/questions/tagged/…

discrete-mathematics 190 questions; if we do not count questions with combinatorics tag, only 90 questions remain: mathoverflow.net/questions/tagged/…

geometry 475 questions; 303 of them do not have other geometry-related tags: mathoverflow.net/questions/tagged/…

BTW I see that several users help with removal of deprecated tags, like this edit by François G. Dorais. He also edited this one and this one.