Not only is Sumo an excellent online image editing suite but it can be used offline [after $20 USD purchase]. When I'm using an ancient system not GIMP-capable I almost always first try SumoPaint.
As I am an ardent proponent of adblocking I would be unlikely to see ads if there were any, but if there are ads they are not placed such that they would hamper functionality.
[you might be pleased with Privoxy for some of your privacy needs. It is an actual freeware loop back proxy capable of page manipulation prior to interweb browser rendering which is very capable of adblocking]