A 100 ah bank isn't sufficient for more than one day of hanging on the hook.
The usable 35 ah goes pretty darn quick, even at 24v.
Like Wind_Magic I think you have your analogy with savings account somewhat off.
The Solar input is like a salary with commission; constant input, sometimes with a bonus. If you plan your array sizing right that's how it works.
At 300w, I plan on 50ah a day, and on good days I'll have 90
To get the same from a portable 2kw generator plugged into my charger (which is a 20 amp) - assuming my bank is down enough in charge to accept a bulk load - I'd have to run the generator for 2 hours to get 40ah (max) then go to absorption charge mode for a couple hours to top off. Let's call that 6 hours of running a generator.
The solar panel just quietly and efficiently puts in 8 or 9 amps a hour, then tapers down to fill it and I do nothing. Even on a cloudy day I get SOME charge, and with 500 ah, I got a lot of days of hang time waiting on some sun shine.
To your original question - yes, portable generators are safe provided you use them properly. They even have a purpose - in my case for running 120v stuff that my 1kw inverter can't handle (air conditioner, bread machine, tools, stuff). As a primary (non- inboard / alternator) method of charging, no way.
It's the exact opposite of your post, you have no autonomy at all, especially on a mooring. You must row out, check the state of charge, fire up the gen, sit there and wait several hours, then row back.
With solar you just have to sit at the yacht club bar and be smug.