To say that you could replace a regular game with a spin-off is quite an exaggeration. Let's debunk some stuff first: Worms Armageddon isn't less lively than WMD. There are WA players outside Steam and WMD has tons of inactive instances running in it's lobby. This game should be cross-platform and it's a fatal overlook by the developers.

Worms Rumble is active to this day despite having it's last update over a year ago. You can find a match easily if you search for Quick Game, Deathmatch or Team Deathmatch. With a substantial amount of players.

I don't mind if Team17 plays around with the concept, market is dynamic and companies have to adjust to the changes and so T17 did when the battle-royale trend had emerged. Such moves resulted in other spin-offs like Worms Crazy Golf and Flockers. The developers have been also following another trend of recycling their games, but honestly who would like that? It does not appease the hunger for the new 2D content well and looking back how they messed up Worms Ultimate Mayhem or Worms World Party Remastered is just clearly no-go, therefore when T17 releases another 2D turn-based game, you can notice that each generation brings some refreshing idea. Reloaded has an advanced map generation, time attacks, puzzles, outfits and AI uses the terrain for it's advantage. Revolution has jiggly water, formations, worms types and a shop. WMD has item crafting and vehicles. Coming up with something new that would somewhat revolutionize the concept but still remain within the beloved by the community standards is difficult and takes time. I see nothing wrong with Team17 experimenting with their legacy if they wish to do so. Worms are iconic and from the business perspective perhaps shouldn't be contained in this forever 2D turn-based cycle. Ubisoft knew it with their Rabbids. Basically, you have to ask yourself what new stuff you would add to the original concept to improve it. Give pointers, don't just open about the wrongdoings.