Agreed.
Most N/A engines do not gain much power without some major internal modifications like performance camshafts and increasing engine displacement. Most N/A engines are as good they are going to get from the factory with some wiggle room to uncap some hidden restricted power caused by the stock intake system,stock ecu tuning and stock exhaust with some simple
mods like performance air filters, ecu tuning and a free-flowing exhaust systems. However, the gains will be very mild at best. Stock version of the air intake,ecu programming, and exhaust is focused more on noise reduction, reliability and fuel economy.
Aftermarket modifications is usually a tradeoff of the three for a small gain in power if done properly.
Like mentioned above; if you want some real power gains for a simple
aftermarket product buy a force inducted engine and tune it for more boost over the stock setting. However, even that can have its negative points too if long term reliability is an issue.