In this season, we only saw 4 (possibly) 5 planets besides Lothal. Kessel, Garel, Stygeon Prime, Fort Anaxes (which is really an asteroid) and Mustafar. Is that enough?
Yeah, not enough planets. But to be fair, TCW had a broader range of characters to use so they could visit virtually any planet they want, here it's just a small band of Rebels.
That said I hope the Base Delta Zero thing forces them to go somewhere less boring/plot convenient.
It's enough. As Fated Xtasy pointed out this show has a much smaller cast with much more limited resources. It makes sense that they can't just go hopping all over the galaxy.
Be patient. I'm sure we'll get more locations as the series continues.