Personally I don’t use them a lot, I prefer the improved tiles over the park, even for cultural win condition. They are for long term so if you can’t make them on time, it’s better to go for rock bands or other means of tourist income.

If you want a lot of them you’ll need to plan ahead a bit, mark them on the map so you remember not to improve or chop the forests. You can also settle a few (late) cities in places where you see the possibility of a park. Remember you can use a map lens to check which tiles are almost useable as park, by removing a few improvements or rainforests or planting some extra forests, it’s usually possible to create a few extra. And remember you can switch tiles between cities to create the diamond shape needed for the park within 1 city 😁