I agree with most of the things you say, ranked choice voting for example would be a major improvement to our system.
Term limits are a mixed bag. There are advantages and disadvantages to it. On one hand it means that you always have relatively inexperienced politicians in office, that have low engagement with their office, making them much easier to bribe or influence since they know that they are going to be gone soon no matter how well they do. It removes some of the incentive to do things that are good for the country instead of what is good for you personally.
I don't really know what you mean about 'open primary' as most states already have a fairly open primary system. I would like to know more about this idea.
Gerrymandering is a bane on our system, and should be done away with, but coming up with a system that enough people agree on is challanging.
Also, the election laws allow for independents to run, nearly every election has some independents running. It is just that they can't win like 90% of the time, and even when they do win they can't accomplish anything, because winning and doing anything after requires coalition, and that is really just another name for party. Almost every political system breaks down into some form of party system. Even ranked choice voting systems trend towards two main parties with a handful of sub-parties that circle those main two.
I do know that implementing almost any of this is next to impossible. It would probably require a Constitutional Amendment, and in the current political climate that is just not happening and if you could change the political climate enough to make it happen it probably would not be needed. That is the problem we currently face, the reasons we need change are the very things that keep the change from happening.
Now to the topic of the thread. Sortition is simply a terrible idea. It has never worked on almost any level. It does not even really work in the jury system. The fact is not many people are really suited to politics. The problems we face today are not simple ones. Finding solutions to them will require a lot of sacrifices, and that means a lot of negotiation to find a happy balance for who makes those sacrifices. That sort of negotiation is a learned skill, and one that is quite rare.