These types of devices definitely have a place.
We rec'd a 200 watt Yeti as a xmas present several years ago. If dry camping, it's very handy as a power supply for our TV and other small loads. If we drive around during the day, I can recharge it via the on-board inverter in my truck. I don't need AC for anything else other than coffee, and I use the gen for a few minutes for that. Using these devices extends our coach batteries and allows us to go a weekend without recharging.
So we find it to be a valuable addition to our energy reserves.
Take note that if you have an battery powered lawn mower like a Ryobi, Greenworks, EGo, etc, you can get reasonably priced PSW inverters for those batteries as well. The one for my Ryobi (Which I have 2/5A batteries for) kept our internet going during a recent 3 day power outage and can run a television for hours. Yes, I know these devices aren't exactly the same thing as a solar gen but it's close enough for us.