Honestly for me the content/gameplay isn't the issue. I do enjoy new DLC's, as they give me motivation to play more, but in general my biggest problem is that it is so difficult to start again. Once the zoo reaches a certain point and my computer starts lagging or if I get a big new idea that won't work in my current build or something I often want to begin anew, but it's so tedious to redecorate everything. Which is in itself frustrating, because I do enjoy the building aspect of the game, it's just that I can only decorate a toilet block so many times before it gets boring.
Thank you for writing something I never knew how to express.
I love Planet Zoo but sometimes I feel like I'm not patient enough for this game.
Even back in the day, when I played ZT and Wildlife Park, it seemed like I had the most fun in the first 3 hours of building the Zoo. I barely completet a Zoo because I always just started a new one. In ZT and WP, that wasn't a problem, but it is tedious in PZ because of the reasons NZFanatic mentioned.
Right now, when I play PZ, I could describe my motivation level with a graph. When I build a new habitat, my motivation is pretty high, but then it drops when I realise that I now have to place food courts, toiletts, decoration... This is the time where I mostly take a break from the game.
I don't know if DLC's will help here. First I was really exited about the new pieces, but now I finished the husk of a giant aztec temple (the inside and the decoration is still not finished) and I just feel exhausted. I didn't even tried the new animals yet.