I imagine that an objective review of the fine print of either the owner's or rental organization's insurance would reveal wording which excludes anything approaching "public" cost sharing. The insurers very fairly perceive a much greater exposure from such dubious activities, and will charge an accordingly greater premium for the proper policy, when the requirements are met.
I have read that Uber has been in difficulty recently, apparently resulting from the less than ideal skill or conduct of some drivers - and that's only cars! There is a vastly greater risk associated with a similar type operation with airplanes. The first time there is a crash, this Wingly outfit will be in for a long nasty experience, and the regulator will feel public pressure to regulate more.
There is a long and sorry history of people "building time" while offsetting or attempting to generate revenue. The options for "sharing" the cost of flying are well understood, new pilots are well advised to stay within the box on this. After all, the genuine, authorized commercial operator, who looses business to chisel charters, may be the employer that new pilot wants to employ them when they have built that piloting time - that could be an awkward job interview! "... I got lots of that piloting time flying unsuspecting Wingly victims, in a rental 172, outside the terms under which I rented it..." in answer to the question at the job interview?!