I'm a bit confused though. Every ride in your parks is making a profit, and most of them even a quite solid one?
The closest one to making a loss is probably the Alpine Slide in Kaiserberg but that seems to be on an upward trend too (and has a bit of a mediocre popularity rating - lowering the price a tiny bit might fix that)
That's because it's an endgame save where the park is already populated and I already did some adjustments to the alpine slide (making the station shorter and have less wagons). Not to mention spending tons of cheated money to place enough trees around to increase decoration rating.
I don't remember the numbers, but the alpine slide originally had a lower maximum income than the maintenance cost but effectively it was only filled to 25%, so it was making huge losses (when I noticed it, it was already at -600 profit).
The bob slide had a maximum income which was slightly higher than the maintenance cost (like $220 maximum income and $180 maintenance cost) and it's fairly easy to fill most of the time, but it's hardly of any use and it's not balance with other coasters which may cost $300 in maintenance but can easily result in maximum income of $1100 or higher.
Keep in mind that you don't just need to do make "a bit profit", you need to get back the money you spent to build it in reasonable time (assuming you want to win the scenario within time limit), plus pay employees monthly.
The relaxing river ride had a similar problem to the alpine slide. In early scenario it's only 25% filled and nets you a huge loss every month even though the decoratiosn are considered "amazing". I spend like $7000 to build it only to make loss from it (in a scenario where people are said to enjoy relaxing rides, mind you).
In the end the core problem is the balance. Some rides just have maximum income 4-10 times higher than the maintenance costs while others need extreme care to even get 20% above the maintenance cost.
As an experienced player (which I consider myself to be now), you just end up building always the same attractions in every single scenario because you know they work best and that makes it boring.
In Kaiserberg, the alpine slide fits the scenario perfectly, so I really want to build it, but if I wanted to beat the scenario without cheating, I can't build it. Some for the bob slide. To beat the scenario without cheating you need to instead start researching rollercoasters right away and build whatever is researched even if it doesn't fit the scenario as well. In Sakura Gardens, even though it's supposed to be a scenario about gentle rides, only the exciting rides are what actually make you able to complete it without cheating, because even in this scenario, the gentle rides don't make enough profit and people still complain about "no high intensity rides".
I played the scenario with the particularly small park (where you need to buy land and can't take credits) and played that one with the knowledge of the game I had accumulated: Only one single low intensity ride, spend rest on good coasters and exciting rides which I know result in high profit and see there, I was already at +$1000 per month after the first year.
But I wish the scenarios where less about knowing which attractions globally work and which are useless and more about figuring out scenario-specific characteristics. Because the campaign is a good 200 hours long and always doing the same thing isn't fun.
And I think the best way to accomplish this would be to first balance the attractions, so everything becomes viable if it fits the scenario.