Zoos and what should we change

As a project within the kindergarten where I do my voluntary work, we took the children on a trip to the Leipzig Zoo, one of the biggest zoos in the world. 
This zoo is one of the most popular attractions in the city and many visitors come every day. I was very curious to see what it would be like inside and whether it would fit in with the zoo concept I have always had: sad animals in too small enclosures, posing still for the public. 
Despite the general excitement, the feeling I got from the visit was not entirely pleasant. It seemed overwhelming to think that these animals would spend the rest of their lives swimming in the same tank, sheltering under the shade of the same rock or hanging from the same trees, with the only difference being the appearance of new faces on the other side of the fence. 
The debate on whether zoos should be closed or not is becoming more and more frequent nowadays. With 700 million visitors a year worldwide, closing zoos is not likely to happen, but a drastic change in the way they operate should be made. 
Most zoos are designed more for the people who will visit than for the animals that live there.
Many animal activists support and suggest the reform of zoos into educational, scientific and in situ conservation spaces with the aim of reintroducing species back into the wild. The only purpose of these places should be the conservation of endangered species, not spectacle or entertainment for humans. 
Some arguments in favour of zoos are that they fulfil the function of protecting animals from poachers who drastically reduce their populations; that they are not only intended to exhibit, but to be centres for research and conservation of endangered species, and finally, to bring children closer to nature and make people aware of the value of these animals. In this regard, it is worth highlighting that of all caged animals in Europe only 0.23% are extinct in the wild; 3.53% are in serious danger of extinction, and 6.28% are endangered. These numbers make us reconsider the real function of zoos. Moreover, a child will learn much more about a lion by watching a documentary about the behaviour of the animal in the savannah or its natural habitat and in interaction with other species, than by seeing it in real life but immobile, as if it were a cuddly toy. 
One of the most criticised points is the space available to the animals to move around or the size of their enclosures, as it is impossible to reproduce habitats according to the animals' needs. Thus, one can often observe in zoo animals what experts call "stereotypies", that is, tics caused by life in captivity that are related to stress or the impossibility of carrying out certain behaviours that are important for the species, and which indicate a lack of well-being. 
It is also worth noting how the life expectancy of many species varies according to their development in captivity or in the wild. For example, elephants have been shown to double their life expectancy outside the zoo.
While researching this topic, I was attracted by an article about an animal rescue centre in the Amazon. What they try to do is to rescue animals, rehabilitate them and release them back into the wild. Many of the rescued animals have grown up dependent on humans as pets, as they have been raised by local people who had found them and kept them as domestic animals, but without any knowledge about the animal's needs, so many of them had great deficits in the development of their abilities or were malnourished and in poor health conditions. 
The centre allows humans to visit, but is very different from a normal zoo. There are no popcorn or food stands, no souvenir shops or places where children can be entertained. No photos are allowed either. It is a place created for the animals and not for visitors.
In this centre they cannot release animals that grew up dependent on humans, as they do not know how to behave in the wild and in many cases are rejected by their own kind. Their purpose is to give back to the animal kingdom what we humans took from it. 
Zoos, however, are responsible for making most species dependent, and turn the animals that live in their facilities into pets by force of human beings.