Are lawnmowers built worse than 20 years ago?

It seems that when I was little, lawn mowers seemed to last longer.
My 6.5 HP Toro is ready to conk out after 4 years. It smokes out of the exhaust, it smokes up through the air filter and it knocks like rocks in a coffee can when I try to cut thick grass. Yeah, the oil is full. The spark plug fouls easily. It acts like a 400,000 mile slant six.
My lawn cutting duties are about 1/2 acre, once a week in warm weather. I don't use this for commercial work.
Do most lawnmowers use all aluminum engine blocks? Its been awhile since I did a teardown on one of these. I seem to remember that one I blew up had no iron sleeve for the cylinder. It was aluminum just like the piston. How the heck could that last with steel piston rings chewing away at the aluminum?
What kind of luck have you had with your mowers?