I just took a glance at the threads on BGDF and it confirms me that board game design is all about mechanic searching.
- Optimal Card Hand Size
- Simple, RPS-like mechanic
- Combat System without dice
- Cooperation incentives in game mechanics?
- Dodge vs Block mechanics for turn based combat system
- A change in taking cover
- Bidding on Semi-Secret Items
- Detection and spotting mechanics
- Approximating the urban planning process & local politics
- Combat with Reverse Deck Building/Pooling?
Creating new mechanics is very hard, so either you search for a mechanic or find a similar mechanic and adapt it to your needs. This is why I am currently another working method (still in progress) in order to avoid mechanic searching since finding the right mechanic for your game can take from 1 days to 1 year which is very unreliable.
One of my friend also told me that war gamers are most likely to become war game designer and they are rarely desiging new mechanics. Instead they re-use mechanics or systems (ex: coins, state of siege) and apply it to a different historical scenario. It reminds me of a war video game that included a map editor to make different scenarios.
What I am saying is that 80% of the game design process seems to be like this (when you start from theme):
"OK, I have this cool theme idea but have not idea how to make it as a board game. So I search for a mechanic by playing other games. When I find something that could work. I test it, try to adapt it. If it fails, I search again and repeat the process until the right match is found."
So this si why all questions looks like "What is the best type of mechanic for that type of game/theme" or "how can I addapt this mechanic for a game/theme", etc.
That is the bulk of the work. Once you have your mechanics and a working game, now you can work on other things which takes the rest of the 20% of the work.