I think that's a pretty silly generalized conclusion for anyone to make--it could very well be the starter solenoid (relay) however it could just as possibly be any of a number of other issues--bad brushes or shorted amature in the starter, poor connection(s) anywhere in the starter low or high current power or ground, a weak cell in the battery, or a small gnome with indigestion living in the crankcase.
"The last time any machine starts and runs properly may have been the last time it will start and run properly"
-George Monroe- a Scottish Stationary Steam Engineer and my maternal grandfather.