great takeaways!
the difficulty one is advice i’ve heard from many experienced devs and it rings true from my own experience. if your game is too difficult for someone they’re not likely to experience all the work you put into it and will probably have a lesser opinion of it.
i totally agree on playtesting as well! there often isn’t enough time for it and it may be hard to find playtesters, but it’s definitely worthwhile if you can. don’t just rely on your own judgement/tastes because what is intuitive for you is often not intuitive for others.
my biggest takeaway from game jams lately is that i work much better in a team than i do alone. for me a team supplies accountability to actually get stuff done, immediate feedback/critique to improve my work, and so much sharing of knowledge.