Far from it, the boxer design is one of the best on the market from the original VW, Porsche, Citroen, Ferrari and others have proven that for decades. That is not to say there has not been some design implementation failures with them, they are a split case engine and with that comes the inherent issue of oil leakage/seepage, it is almost in their DNA. Anyone that owned an old British bike knows if it didn't have a drop of oil under it, the engine was probably out of oil, they were also split case engines with no pan.
The positives of the boxer are many, they are very smooth, low vibration and rev freely. Thinking back to the old VW and Porsche engines their engines had to ba removed for anything more than very minor things the Subaru is not bad, the engine is out in 2 hours and is very easy to repair out of the car. Personally I wish they didn't go to a cam chain instead of the belt especially recommending thin oils. Just another leak point and more complexity, the belt was an easy job, it didn't beat the oil to death and are quiet. Going to an open deck instead of the closed deck didn't do anyone any favors either, that alone was more than partially responsible for the HG fiasco.