You misunderstood. I’m aware KDE doesn’t support languages other than QML and C++. I’m saying this is probably a choice on their behalf to make things easier to maintain. Whether or not this choice is good is up for debate, but I don’t think it is the result of a lack of funding.

As for where your money goes, their donation page has a section on this which also links to annual reports. Some larger KDE projects do have their own donation buttons (like Kdenlive and Krita), but most don’t. A lot are just too small for it to be worth it, but this is still an area that can be improved. As for the “KDE Team”, that’s a pretty nebulous concept. I don’t think there is one, officially. KDE is a community of mostly volunteers working on KDE software. Most of the ones paid to work on KDE aren’t paid by donations, but are hired by third parties to work on KDE, like Blue Systems or Valve. Right now I believe most of the money is spent on infrastructure and events. Afaik, most of the people paid directly by donations are Krita and Kdenlive devs, since that’s what they raised their own funds for. KDE wants to start hiring more developers tho and I imagine their successful Plasma 6 fundraiser will allow them to do this.

Also, keep in mind the fact that Mozilla software including Thunderbird is just significantly more popular than pretty much anything KDE makes. Yes, KDE is infinitely larger in scope than Thunderbird is, but Thunderbird sees a lot more mainstream professional use than any piece of KDE software and that’s what gets you money.