I don't know if the inability to link to other sites is a major issue in general, clearly it is for some and I can see arguments for and against. I think I would make the point though that there is a lot more wrong here than the inability to link and it would be wrong to suggest that there is a really simple answer for Rendo.

The off-site linking has gotten ridiculous as they decided to change the rule from "only links to sites that have marketplaces are prohibited" to "no off-site linking to freebies because we want people to upload freebies to Rendo instead" This new rule was posted JUST TODAY.

https://www.renderosity.com/mod/forumpro/?thread_id=2899703

In the TOS, we now have a new addition that states we no longer accept off-site links. So, unfortunately, you're unable to post off-site freebies. That may come as a disappointment and shock to some, but we'd really like you to start focusing more on linking to YOUR FAVORITE FREEBIES from OUR site.

Personally, I hope this backfires, but I don't have much hope for that.
The absolute stupidest thing about this rule is that it makes the forums FAR LESS helpful-- let's say someone says they remember some python script from long ago that allows you to do X, and wish they had it. Someone could then post the off-site link to the script, esp. useful if it is uploaded to someone's Dropbox (making it difficult if not impossible to find using search engines like Google and Bing)