The report looked at three sources - one pay and two free. They came up with a number of results but I think they largely missed the point.
Their bottom line conclusion was that 'Overall, reviewers rate most of the materials as “mediocre” or “probably not worth using”.' They also didn't seem to find that neither the for profit or free sources were universally better.
The one thing I can agree with though is that a consistent rating system for the types of resources found on these sites would be very helpful.
I think the main problem with the report has to do with what they were looking for. They concluded things like the resources didn't line up well with standards, didn't have good assessments, didn't address cultural diversity and a few other "didn't dos," As I said, I think they missed the point.
It felt to me that the reviewers were looking for rote experiences. Download a lesson and follow the script.
In spite of what reformers would have you think, that isn't teaching. A teacher new to a class might start with a well worked out curriculum and largely follow it verbatim but as they develop their chops they'll want the curriculum and all related materials to become their own.
A downloaded resource, taken as is, will likely not address a specific classes cultural diversity, at least not more than in the general sense because it was designed for the authors class and that's a good thing. It's up to the person doing the downloading to take the resource and then adapt it for their students in their situation. This is why most of the items that the report considers bad to me are both inevitable and fine. There is no universal lesson that you can cut and paste to all schools. To expect it is rubbish.
On the CS side, there's a good amount of sharing of materials as well as providers well, providing content. Some is free some not but there is a lot available. Forgetting about whole curricula resources, three lesson / experience sites I'm reasonably familiar with are the SIGCSE Nifty Assignments and now the CSTA's corresponding project along with Engage CS.
The biggest problem with the Nifty sites is that they're arranged chronologically by the conference year they were presented. There are no tags nor easy way to search. Engage CS gives you some level of searching like for course level, keyword, resource type, and more.
The sites present resources in a format that's superficially consistent but the truth is, once you get past the headings they can be written up in radically different ways.
To me, that's not a problem. Each resource was written by some educator with the intent of sharing but since each author is unique so to will be the content they produce.
The real value of all these resources are to get ideas - lesson motivations, code samples, project ideas etc.. Sure, I wish they were more discoverable via search - better tagged and yes, even better rated but the value is from reading what some other teacher has done and then pulling out aspects that can work for you.
I've rarely used a Nifty Assignment nor something from EngageCS explicitly but I have gotten value from both sites (CSTA Nifty assignments are newer and I've been at all the CSTA sessions so haven't actually used the site).
Would I ever use a resources "as published?" Perhaps - if it was really well aligned with how I do things.
Would I pay? Probably not. I'm not against paying for resources from a philosophical point of view. Charge a fair price and give a reasonable assurance that what you're selling has value and provide some value beyond the free sites. I haven't used Teachers Pay Teachers and probably won't look at Amazon's thing when it's launched but to me, they would have to bring value in terms of curation and search. If they do at a fair price, then they may be worth using.
When I started teaching there was no public internet. None of this existed. Teachers kept binders or books of lesson plans and if you were lucky you could borrow from a friend or colleague. New York's DOE at one point had a few teachers in each subject area submit lesson plans for "lesson books" which they published for each core subject. My chairman wrote some of the math ones and those materials largely got me through my first year.
Today we have an embarrassment of riches. That comes with the price that we have to actually read and evaluate all of the materials we're presented with but I'll take today's resources over what I started with any day.