- Animals lifespans/gestation times being incredibly wacky in ZT2 irritated me no end. Most modded animals were fine with realistic lifespans in terms of years, and then you have base game lions dying in 2 ingame years 
Then as others have said the issues with animals breeding exponentially. In larger zoos, this makes things like separating animals by sex really difficult, because you keep having to check in whenever animals die of old age to top up and in challenge mode with the animal roulette this was really just irritating.
- Thanks to various bugs and placement issues, not being able to find very obvious water/food bowls that weren't colliding with anything -> becoming sick and dying = huge pain for the same reason, I felt that to have a nice enclosure that I'd built to look exactly how I wanted it I had to sacrifice the animals surviving for longer than about 30 minutes of playtime.
- Zookeepers sitting around doing nothing on the benches you placed down for guests, so guests can't sit down and complain about having nowhere to sit. Staff being relatively useless in general, especially if we don't get a zookeeper mode or some way of manually replenishing food bowls/cleaning up poop/etc.
- Guests not being able to see animals - even if you can, very clearly, see the animals from the exact same vantage point in zookeeper mode. One very specific one that irritated me was not being able to see marine shows from an elevated path because you couldn't make very nice looking show tanks, but that's a very specific gripe when I don't think we'll get similar features in PZ
- Glitchy elevated paths, oh lord. When you accidentally triggered that glitch that made a very small section of terrain suddenly drop into a deep, sharp cliff that no amount of terraforming can fix or cover up.
All around I feel that ZT2 even modded made for a very nice zoo design experience, but is not so good for playing an actual zoo simulator due to all of the bugs. As soon as you try and run a zoo with animals in it, and god forbid open it up to guests, the problems just roll in and you're hearing that alert sound over and over and over and over... So much that whenever I play ZT2 I end up missing important messages like animal pregnancies, animal deaths, births, etc. because they're drowned out by "can't reach x" and "guests need more x" messages all the time.
Then as others have said the issues with animals breeding exponentially. In larger zoos, this makes things like separating animals by sex really difficult, because you keep having to check in whenever animals die of old age to top up and in challenge mode with the animal roulette this was really just irritating.- Thanks to various bugs and placement issues, not being able to find very obvious water/food bowls that weren't colliding with anything -> becoming sick and dying = huge pain for the same reason, I felt that to have a nice enclosure that I'd built to look exactly how I wanted it I had to sacrifice the animals surviving for longer than about 30 minutes of playtime.
- Zookeepers sitting around doing nothing on the benches you placed down for guests, so guests can't sit down and complain about having nowhere to sit. Staff being relatively useless in general, especially if we don't get a zookeeper mode or some way of manually replenishing food bowls/cleaning up poop/etc.
- Guests not being able to see animals - even if you can, very clearly, see the animals from the exact same vantage point in zookeeper mode. One very specific one that irritated me was not being able to see marine shows from an elevated path because you couldn't make very nice looking show tanks, but that's a very specific gripe when I don't think we'll get similar features in PZ
- Glitchy elevated paths, oh lord. When you accidentally triggered that glitch that made a very small section of terrain suddenly drop into a deep, sharp cliff that no amount of terraforming can fix or cover up.
All around I feel that ZT2 even modded made for a very nice zoo design experience, but is not so good for playing an actual zoo simulator due to all of the bugs. As soon as you try and run a zoo with animals in it, and god forbid open it up to guests, the problems just roll in and you're hearing that alert sound over and over and over and over... So much that whenever I play ZT2 I end up missing important messages like animal pregnancies, animal deaths, births, etc. because they're drowned out by "can't reach x" and "guests need more x" messages all the time.
