I'm sorry you feel this way about the community. I have myself been very busy recently and much less available to help out. There may just be similar conditions with other contributors. Sometimes it's not enough, but we all do the best we can.
It's sad this issue was not caught before. It was probably introduced very close to the release because that feature is heavily tested on i18n.tiki.org.
I investigated a little bit and there are in fact two issues at play. One is that the permission was mis-attributed to feature_multilingual. This is part of an effort to simplify administration by removing elements that are not useful from the interface. Sometimes, too much gets removed. Sorry.
The second one is that the global permission check did not appropriately handle a specificity about admin privileges.
Both issues are resolved as part of branches/8.x and will be part of the next release.
In the mean time, you can enable feature_multilingual (and maybe clear the cache) to access interactive translation.
Alternatively, you can just update if you use a subversion installation or take in the fixes in commit r39181 and r39182.
Have a good day.