Exactly! Sinnoh was the perfect Pokemon region. It didn't feel like it was horribly confusing but you definitely had a lot of space to explore (I've come to realize a lot of Unova did this too, after I played BW and BW2 again last year). There were so many optional little secrets around Sinnoh that, especially after my last playthrough (I've played Platinum like 5 or 6 times in the past 5 years) it just kept me playing and playing after I beat Cynthia. It also had a fantastic roster of Pokemon (210 is really impressive and they picked some REALLY good ones). It just felt so adventurous compared to Sun and Moon which felt WAY too linear and empty.Totally agreed there. Platinum is the best so far objective (my gen 1 love is 50 % nostalgia). I am therefore glad to see that this region seems to take things from the Sinnoh region. However, also as you said, Sun & Moon was a disapointment and I think this was mostly due to there being so little space to discover on your own. You were guided constantly. This was exactly what made Platinum (well, one of the things) so great; it felt very spacious. You could discover all sorts of corners and creeks. Let's hope the new games are anything like that and do not follow the Sun & Moon route! The fact that gyms are back is already a good sign.
Gyms being back is already a good sign and I think the region looks really fun, I just do hope that despite it being detailed it doesn't hesitate to allowing the player to explore hidden areas and have optional sidequests. A good postgame, which is what a lot of recent games in the series lack would also be really appreciated. I want something like Platinum or BW/BW2's postgames. More areas to go to after the game, sidequests, all that fun stuff.