So I said it before as an angry rant to people complaining that it's taking so long, this time I'm going to flip it on its head... I think these projects are a first for a lot of these devs. It's so so easy to underestimate the time anything will take in a project especially with so many moving parts. And as Magicnuts has said, throwing money at the problem doesn't always solve it.
Think of it this way: Building a house can take 20 people 1 month. 40 people gets it done in 2 weeks. 60 people it goes back to taking a month. Not always does adding people help, and in some cases it can detract. If they hire Jimmy the Intern to do some of the art and he comes back 3 weeks later with the art in a completely wrong style or some other mistake... Add 3 additional weeks to the workload because it needs to be fixed.
On top of that I think there's also the pressure. You mentioned DPC has 13.5k supporters. That's 13,500 people who weigh on his shoulders every time he makes a render, writes a scene, programs a minigame. 13,500 people who it might feel like he's disappointing and it can cause a crippling bout of perfectionism, imposter syndrome, all sorts of stuff. I'm not saying it isn't a problem, but I'm also saying as outsiders peering in we aren't privy to everything going on.
DPC releases meaty updates. What a Legend has full character arcs released in the updates and they're not small either - in addition to it being hand drawn (I'm sure there's an argument to be made for 3DCG games rendering every scene frame by frame vs. paperdoll systems maybe evening out time spent but that's a whole other thing). Yes, they skew to go longer... but it's not like they all start falling off. I believe these should be treated as a case-by-case basis.
Magicnuts is very transparent and gives frequent updates. Correct me if I'm wrong they also said this update was larger than the last? So the time it's taken isn't really that bad imo. If they keep backsliding and taking an additional month every update with no increase in quality, size, or anything like that... Sure. But this is literally the first time this has happened. Let's not start frothing at the mouth and beating good devs with sticks because we scheduled a day off work to jerk off to a release that never came.