Devs are their own bosses. There's a lot to be said in favour of this when it comes to creativity & no-one in their right mind would want to hamper the process, or try to artificially limit artistic freedom but if motivation is a combination of "carrot & stick" then the current Patreon model is not working well in the interests of many patrons. [I am a Patron but not of AWAM]. Some form of payment by results, (PBR), or a stoppage of payments whenever huge delays occur are possible answers. At present there's not much of a stick in play. This is in stark contrast to much of the working world, where there's plenty of stick but often just a piece of string where the carrot used to be.
At present the Patrons are perceived as contributors to a project, giving payment in the hopes this will inspire artists to greater heights. They are likened to "patrons of the arts" as they've appeared, in the modern sense, at least since Renaissance times. Obviously this isn't a very effective approach when it comes to volume &/or timeliness of output.
Patrons have just two options, i.e., to pay regularly, or not to pay. I sometimes choose the latter when a Dev's creativity flags. I also return if it picks up. If sufficient Patrons carry on paying when nothing is happening then it's possible that a 'comfort zone' can exist where money rolls in but work continues at a leisurely pace. Within the Patreon model as it is right now it's up to more Patrons to become pro-active & start withdrawing their sponsorship far more often. If this doesn't happen, IMO, things can only get worse, or stay the same, unless a Dev decides otherwise.