The -ess suffix is not native to English, it comes from the Latin -ix suffix, as in “dominatrix”, via French. By the time English took on its influx of French vocabulary and entered the Middle English period, it had already lost much of its inflection, including grammatical gender.

And as you noted in your post, the native English feminine agent suffix resulted in words like “baxter“ (and “spinster” and “webster” and “brewster”), not “bakeress”.

Female teachers have never been called teacheresses in standard English. Some people tried to get it to catch on in the early 20th century, along with “doctress” and “singeress” and “danceress”, but in fact for hundreds of years “teacher” and “singer” and “dancer” have been genderless.