I see modding as this huge interconnected web of ideas, skill, knowledge, and the mods themselves of course. I see paid modding as one of the greatest threats to modding because as soon as payment becomes mandatory, or expected, or the baseline, that web gets obliterated.
The mostly holistic Collaboration we enjoy (and benefit from) now disappears. How many new modders will we preemptively cull or turn away because the entry barrier is a steep learning curve behind a paywall? One of the best ways to learn is to deconstruct features you wish to emulate or re-purpose. Once mod content becomes monetized mod authors are heavily incentivized to obfuscate all their techniques and source code. Without new modders or widespread collaboration the "web" stagnates, breaks down, then dies. Basically once begun we enter a negative feedback loop resulting in self-destruction. At that point it's entirely possible for the absence of the modding scene to be reflected in sales, thus potentially compromising the future of the franchise.
We cannot begin to understand the influence even one new modder can have on the entire scene (or what other skills they may be bringing to the table). How many times do you think someone's "Help" post (even if unfinished or unresolved) has eventually contributed to a solution for someone else? I've been modding for years now and it happens to me all the time.
I agree.