Interstellar travel is not impossible, it just takes a long, long time (assuming there is no work-around to the FTL barrier). But I agree there are probably no Type III civilizations and probably very few, if any, Type IIs. My guess is most scientific civilizations will lose interest in further technological development once their perceived security and comfort requirements are satisfied.

Even if interstellar travel takes very long amounts of time, advanced civilizations may work on very long schedules. We can't expect they are as impatient for results as we are, or that they are as interested in progress just for for progress's sake as we seem to be.