Is the Turkish coast worth a separate trip?
Yes, if you want it to feel like more than a beach add-on. The coast works best when it has its own rhythm: boats, late dinners, short drives and days that are not recovering from Cappadocia transfers.
Answer
The Turkish coast can be a highlight, but it is not at its best when squeezed between long inland jumps. A rushed coastal stop often becomes one beach, one transfer and one tired dinner. Give it time and the payoff changes: boat days, old harbours, ruins, swims, coastal roads, long meals and bases that feel different from each other. For a short first Turkey trip, it can be smarter to skip the coast and come back than to add two ornamental nights. If the coast is the point, let it be the point.