As other have mentioned SWA has a really odd no policy policy on seat saving. You’re just as likely to get scolded for moving somebody else’s things as you are to have the flight attendant side with you.
I honestly wouldn’t let it deter you. I’ve flown Southwest a fair amount and have had exactly one instance of seat issues. I find the boarding process on the legacy airlines way more tedious even with assigned seats and I usually fly 1st class because I’m fancy and awesome (lol not really, I’m willing to pay extra so my invaded space bubble anxiety is a little lower). Plus the flexibility of changing your tickets or cancelling on Southwest cannot be beat.
The bolded is why I absolutely LOVE flying Southwest, and have accumulated a ton of points in addition to a companion pass. We have flown them for years and I love the point system. I have booked, cancelled, rebooked so many flights with them. I think if they ever changed that part of their airline then i would consider flying others. We did recently fly Jetblue because they depart out of an airport slightly closer to us than Southwest and Jetblue was fine but nothing over the top wonderful. The TVs in the seatbacks were nice but only worked for one of our flights.
We never use EBCI anyway, as I usually can get a good boarding spot by checking in 24 hours before on the dot.