Chubby cuddlebot Lemma!

I don't have any ideas outside of the ones you've mentioned, but I totally agree that tools, code reuse, and asset reuse can save you so much overhead when starting a new project.

As an example, things like menu sounds and icons can often be reused easily! And spending a little extra time to build a sturdy class that handles background music or scene transitions that you can just pop into every new project is really convenient.

A lot of your examples really highlight the idea that, the longer a person works in games, the more efficient they'll (likely) be at it. Aside from being able to re-use work from previous projects, experience means being able to spot potential problems before losing too much time. I think that's something worth keeping in mind, and hopefully encourages people to stick around, keep making, and keep learning!

as an indie dev with my own reusable tools/engine and rollback netcode implementation, i totally agree with this advice! i've been a bit slow getting started because i'm learning art and music as i go, but hopefully i'll accelerate soon.

i personally find the japanese indie/doujin scene to be the most inspirational place to see examples of these strategies in action. zun made tons of touhou sequels, french bread and twilight frontier made tons of fighting games and similar games, platine dispositif made tons of shmups and similar games (most of which feature the same pumpkin enemy sprite), and so on. there are plenty of prolific indie visual novel devs all over the world too, such as @nomnomnami and @npckc.

another strategy is that if you want to build a large game with several mechanics or modes, you can slowly build up to it by making and releasing some smaller games that are a subset of the larger one. recettear is a big game with dungeon combat and rpg mechanics and story scenes and item shop gameplay, but its developers built up to it by making duo princess and chantelise first. so by the time they started making recettear, they already had all of the dungeon and rpg gameplay (including the enemy and item assets!) and the cutscene tech. for more examples, pixel made ikachan before making cave story, and edelweiss made fairy bloom and fairy bloom freesia before making sakuna.

i suppose this strategy is technically just a combination of code reuse, asset reuse and genre specialization, but i personally find it helpful to think of it as a strategy for staying productive while switching genres or making large games: make the smallest game possible when switching to a new genre, and build up to large games by creating subsets of them as their own games first.

I really feel you on 1, 2, 3, 4, 6, & 7! My recent games have only been possible because of the efficiency gained doing these and as a bonus each one is leaps and bounds better than the one before it since skills, knowledge, and many hours of work get carried forward!