These are needed but not limited to. It means just because of having all these will not guarantee big success for a coin. Have seen many good concept based coins got failed due to lack of supporters. It means devs must work on convincing new investors all the times. If a project fails to attract new investors then it may get heavily dumped and the slowly will get delisted from exchanges.
When a project remain attractive for new investors and for existing investors to keep holding their coins/tokens?
It will remain attractive when new features being added and roadmaps is getting updated regularly and when devs interact with crypto community in social media etc.
Overall, active dev team is the most important requirement for success of a coin.
It is not easy to convince people to join and stay there, I have been part of few projects and I can tell you that people come in, increase the price, sell at the top and then drop the price so much that in the end you have nothing else, you end up basically a coin that dropped over 80% with nowhere to go because it used all the marketing budget.
Unfortunately in crypto world unless you go over this huge hump and become wildly known and loved or you have insane amount of money for creating one, you are going to be just a project that people look to make a quick buck and nothing more, that is the only thing and there is not much more to it at all. You can't stop people from buying, and you can't stop them from selling if people want to make a profit they will do it and they may not care at all what you want to achieve with the project as long as they can make a quick profit.