Your positive conclusion on the bird house really surprised me. I found it extremely disappointing upon my visit a couple of years back - essentially a continuation of the mid-20th Century zoo house concept as present in Berlin's cat- and ape-houses. Endless rows of largely barren cages. Your verdict would make it seem that the renovation of the house - only a few years after it was inaugurated - has led to substantial improvements. Do you - or anyone else - have pictures of the bird-house in its present state?
I am also surprised by your overall negative verdict on indoor holdings in Europe. In fact I would have stated quite the opposite: in Europe (Western Europe where there is regular snow in winter, to be more precise) one can likely find the highest density/frequency of high-quality indoor holdings anywhere in the world. Of the European zoos I've visited, I think Basel, Zurich, and Vienna show the way, of the ones I haven't, I would guess that many Dutch and German zoos would follow in kind. There is a long list of relatively recent European indoor exhibits that are imo well executed from both a visitor and animal wellfare pov and/or have set standards in one way or another, e.g. Burger's (Desert, Bush, Mangrove), Vienna (successful renovation, repurposing of historic buildings, e.g. bird-house, monkey-house), Zurich (Masoala, Kaeng Krachan, but also e.g. the lion house - which used to be a Berlin-style stamp collection of cats), Leipzig (Gondwanaland), Basel (Etosha), and countless more. The US and Australia seem to focus much more on outdoor exhibits with indoor holdings frequently being off-show. Asia - including Japan - from what I have seen still lags far behind Europe in exhibit quality generally (with certain exceptions) - but especially indoor holdings.