You are still missing the point.
There is a difference between having an inadequate (or, below average, outdated etc.) enclosure as a legacy from a bygone age, and building an inadequate (etc.) enclosure from scratch.
As most of us know, zoos cannot replace all exhibits the second they become outdated. We also know that relocating animals is stressful, sometimes risky, and requires adaptation, and in the case of old, surplus or hybrid animals, relocation may not even be possible. The choice then, often, is between euthanasia, moving behind the scenes (usually in worse conditions than on show) or maintaining the current situation (which is also the one the animal has lived in for often years or decades). Often renovations are planned somewhere down the line, or the enclosure is planned to demolished if the current inhabitant(s) die(s). All these conditions temper criticism and foster some sort of (often reluctant) acceptance for the current state, especially when it comes to a topic so nuanced and multi-dimensional as animal welfare.
If one is building an inadequate exhibit from scratch, all these conditions do not apply. You are already moving animals, you know modern husbandry standards, and the point that not everything can be changed at once is also not valid here. This is not only true for Pairi Daiza, but also for more established zoos. Burgers' elephant stable is outdated, but it was build in a different time, the zoo purposefully only houses two elderly females, and unfortunately one cannot simply wish upon a star to renovate it in an instant. And its inadequacy didn't come in an instant, but the realization that is not up to standard has grown over the years. I can accept that, though I am glad they're planning to improve it. But if they were to design and build a stable like that today, or purposefully bring in an animal and put in an inadequate enclosure, I and probably everyone else here would rightfully criticize it. Even for one of the most beloved zoos by members of this site.
Pairi Daiza has build entirely new enclosures that seemingly* walk the wire between acceptable and inadequate - which means they'll probably be considered inadequate within a decade or two - and sometimes even below that. Or they finally move an animal out of an outdated exhibit, only to replace with an animal for which it is just as bad or little better. This is not legacy from a bygone time, they should and could have done better. This is especially glaring in this situation, because Pairi Daiza seemingly* has more financial resources than almost any other zoo.
* Of course I do not know all details, so I won't make any definitive judgement.
