I do not think that Galatasaray "needs" Talisca, nobody would say no to a good player of course but spending that much money on a 30 year old player doesn't make sense when you are already winning the league, and they are 6 points ahead, and looking like a much better team as well.
Also, if we are looking at what they need, I would say that getting a wing back would be a bit more important for them, they have been missing a left back since Angelino left ,and they still haven't found a good replacement. They bought someone but never seen him play before, dude is injured for the whole season.
So all in all, Fenerbahce makes much more sense, he would fit there amazingly, he would contribute right away, and would get them to better places. Right now they have a lot of problems at defense if you ask me, trying to get even more offensive players makes no sense, if they are willing to spend that much money then I would suggest getting a defender instead, or wing back for them too, to left back, but if they insist, Talisca would help too.
Yeah, you've said it all, Galatasary have so much attacking options right now that some are currently struggling to get minutes under their belt and are good players also. They are option in that right win who will make similar contributions just the way talisca would, let take ziyech for example, he is very similar to talisca in terms of play and creativity, and ziyech is not an injury prone player so adding talisca to that squad is just going to be too much and another big reason I don't think Galatasary should go him is the wages he would want to be paid. There are alot of big names in Galatasary now who are earning 80k above so adding talisca to this list who seems to be a surplus would never be good for business
Fenebarche seen to be the right place for me and for sure he will get alot of playing time there and just like you said he is going to fit right in. Saint maximin on the left side with him on the right side will be wild. He is a very good player technically and also have a very gifted left foot. Fenerbahce needs to improve their squad this January if they really want to compete for the title. Talisca will be a good add up to the team. Fenerbahce is the perfect place for him in Turkey.