First of all, I want to state that this text represents my fears and my opinion based on my personal experience. It is not intended as an attack on anyone or anything.
Although the idea of a Drupal template marketplace seems like a good idea to me and could be a good boost for Drupal as a product and therefore for the Drupal community, these are my doubts, fears, or a mix of everything.
When we talk about a Drupal template marketplace, the WordPress marketplace comes to mind. It's true that this marketplace works and has possibly been one of WordPress's successes in becoming the product it is today, as it allowed someone without technical knowledge to have a beautiful and operational website.
But we have to take the following into account: a high percentage of sites built with WordPress only use the two content types that come standard in WordPress: page and blog. Having such a basic and simple content architecture makes it easy to create themes that can be sold, since the fields used are known and therefore it doesn't pose any problem.
To be able to do something similar, we either create a marketplace solely for Drupal CMS, or Drupal themes will only use "Article" and "Basic Page," which could be an option, a kind of Minimum Viable Product (MVP). However, my suspicion is that both Drupal CMS projects and Drupal in general will transcend the content architecture that these two products offer.
From my experience, Drupal usually tends towards content architectures that adapt very well to the needs of projects and do not usually remain in the basic proposals.
How can we overcome the particularity of Drupal having content architectures tailored to project needs and at the same time work with a theme marketplace? I believe that a solution would be recipes and the SDC module.
If the community builds a kind of PSR (PHP Standards Recommendations) for content type recipes that can be installed as dependencies in projects, and in turn these recipes include an SDC for each element, it would make things much easier.
On the one hand, these recipes would make it easier for site builders (and also for end users with less technical knowledge) when creating a project, as they could navigate between the different content type recipe options and choose the ones they need for the project. As I mentioned above, these recipes, in addition to a standard content type configuration, should have an associated SDC so that, without needing to buy a theme, they at least have the necessary HTML to be basic but correct.
On the other hand, with this standardization, what will be achieved is that the themes programmed for Drupal will be more consistent with the project's content types. In fact, it would be interesting for themes to indicate the content types they style in their theme definition, so that a buyer can search among those that interest them most.
Another of my fears is that the people who program the themes will move the backend logic to the Twig templates, either through Drupal community modules or through code they have programmed themselves.
I don't have a solution for this. Perhaps a product rating and comment system, but these types of services eventually become very biased. Perhaps an agent of an LLM model that analyzes the code and can publish comments about it, but this would also be complex and costly.
These are my fears and concerns, and what I seek with this exposition is not to scare anyone, but to work with the community to find the best way to build a healthy marketplace that helps the development of Drupal as a community and as a product. (editado)