You didn't clarify xtempore that poeta can also refer to a female poet in which case it would be written "la poeta". Poetisa is an alternative word for a female poet. The RAE should be correct.
poeta. (Del lat. poēta, y este del gr. ποιητής). 1. com. Persona que compone obras poéticas. 2. com. Persona dotada de gracia o sensibilidad poética.
When does the gender of profession words change? Last question I got wrong because I didn´t think both las soldatas and los soldatas could be correct, and this one I get wrong because poets can apparently only be male. Is there any pattern or do you just have to memorize it?
RAE apart from confirming that "poeta" is both masculine and feminine was no help here - at least not to me - however the implication is that the masculine article (el) should be used when referring to a male poet and the feminine (la) when the poet is female. In that case either "el" or "la" should be acceptable. Maybe there is a rule in Spanish which says the generic form must always be masculine - If anyone that can point to this - I would appreciate it?
http://lema.rae.es/drae/?val=poeta poeta. (Del lat. poēta, y este del gr. ποιητής). 1. com. Persona que compone obras poéticas y está dotada de las facultades necesarias para componerlas. 2. com. Persona que escribe obras poéticas.
Spanishgrammargenius (http://www.spanishgrammargenius.com/spanish_masculine_feminine.htm) says this:
Most nouns that refer to roles or jobs that end with “ista” or “eta” don’t change their ending along with their gender:
El dentista= the male dentist La dentista= the female dentist
El poeta= the male poet La poeta= the female poet
El turista= the male tourist La turista= the female tourist