Well, if nobody else is going to say it, I will.

Big box bikes are usually made of mild steel or the lowest grade of "hi tensil" steel. Sometimes they are heavy guage aluminum. All this means is what ever material they are made of they will be heavy compared to LBS bikes. "Heavy" takes some of the fun out of riding, but doesn't mean they are not functional. The components are decidedly low end, but again they are functional if not durable.

The worst sins of the big box marketers is the absolute total lack of quality assembly and fitting. They pay highscool kids a couple of bucks apiece to stick those things together so they can be displayed on the sales floor. They have no concern whether the bikes make it out the door before parts start to fall off and they wouldn't even know how to fit a bike to a rider. Couldn't fit it any way since they don't have different sizes.

In my local big box retailer there are normally about 50 full suspension fake mountain bikes, 20 fake BMX bikes and kids bikes and then maybe 4 or 5 decent hardtail Schwinns or Mongoose semi hybrid/fitness type bikes. Then there is usually 1 or 2 e-bikes. I would absolutely not even give the full suspension bikes a second look. Those are all crap. It's possible to make a decent bike for between $100 and $200; but not with full suspension.

They know those suspension bikes are crap, they even put a disclaimer on them warning you to not ride them off road. I have actually seen those frames come apart in mid decent when somebody did not head the warning. A painful lesson.

Having said all that, those 4 or 5 Schwinn hybrid/fitness type bikes are fairly good bikes, just know you will have to reassemble it when you get it home.