2/3 of issues you showed are purely formatting concerns, so I'm not sure what needs to be tested there. "test.written" refers to test being written in a testing framework, "status.tested" means that the described bug was tested in multiple development environments and confirmed. So your remark is slightly off the base.
Small number of dedicated contributors: historically, Rebol (the ancestor of Red) was developed by Rebol Tech company in a closed manner. So, IMO there developed a particular community mindset, where everyone just lets the Boss do the job and watches the action from the tribunes.
Another reason, like I said elsewhere, is the fact that Rebol never became mainstream, hence there isn't much contributors ready to provide the code of acceptable quality.
Lack of comments and such: in the early days, Red planned to be minimal and bootstrapped early, so the whole codebase was written in a throw-away fashion, with no comments or afterthoughts. As the project growed and roadmap changed its curves, community started raising demands (macOS View backend, new datatypes, supporting other platforms, the list goes on), so the "quick bootsrap" plan was ditched, but the code remained. This is a stumble block for other contributors, which, alas, will be moved away only after 1.0 is reached.
"Simplicity and fun" is completely off the point though, but I get what you say, even with a snarky tone. "Simplicity" here refers to the use of embedded DSLs, in which it is generally easy to express ideas suitable for a particular domain, and to "self-contained small toolchain" goal of the project. So, expressing ideas and developing them is rather simple, once you got the hang of the language.
Reading Red code requires a prior knowledge of function's arity and evaluation rules; ambitious projects require knowledge of multiple dialects and thorough understanding of core concepts; dynamic pieces (i.e. metaprogramming) can be challenging, unless you're coming from Lisp or Forth camp.
Runtime is written in Red/System dialect, which requires C-level skills to write. Red and Red/System share the same syntax, but require a huge mental leap to switch the context (Lisp vs. C dichotomy) - another 2 cents to your "lack of contributors".
I'm not a fan of "Red is simple and for everyone" sales pitch either - it's misleading at best, sets the wrong expectations and usually comes from people who barely clocked 1 hour in REPL tinkering with available View examples.
Hope that answers your concerns, more or less. If you want to alleviate them more quickly - drop by our community chat and start contributing piece by piece ;) Cheers.