You will likely see many complaints online regarding Coinbase and Gemini. There are many reasons for this, but they are viable options.
Unfortunately, you will be required to provide KCY documents, go through an approval process/experience wait times, fees, account/purchase limits et al…
While there are a few other options available to US citizens, those options may not be ideal, especially if you are looking to purchase large amounts of crypto. Most people initially opt for one of the aforementioned simply because they operate inside of the US, which provides a layer of security, as well as the fact that bank wire transfers can be used and crypto can be purchased without any fees, directly on the exchange.
I remember experiencing a great deal of frustration with both of these services when I first started. I am sure that things are even worse now for new accounts. Unfortunately, I do not foresee many improvements with regard to customer convenience due to over-regulation, compliance and restrictions etc., but I am hopeful that better alternatives may become available once we see wider adoption for cryptocurrency in the future. I do see other countries leading the way, however, while the US falls way behind, for obvious reasons. So, we may have to continue looking offshore as things continue to play out here in ridiculous fashion.