Alpaca is great! As far as brokerage APIs go, theirs is top notch and a breeze to code for. The founders are also really responsive and helpful.
I know this because I wrote an app that connects to Alpaca accounts (as well as other brokerages) to help people build their own custom index funds [0]. It only took a few weeks to build our Alpaca integration, whereas other brokerages often take months/years just to get access to their APIs.
I love M1! But I have come to hate their "tech". Obscure URL's (what was that stock you looked at two days ago? good luck finding it in your history!), broken watchlist, can't explore adjustments to a pie (such as two windows to submit/revert a pie change), have to contact support to pause trading, backtesting breaks if stocks are listed <5 years ago... they recently added dark mode to their app with terrible contrast of red/green (the green looks black in white mode so you have to use dark)
I feel like their UX priorities are screwed up big time. But as a platform, they're my favorite as far as concept/functionality.
Selling order flow isn't "selling the poor out". Reg NMS literally requires brokerages to route your orders to where they will get the best execution price. In general you as a retail investor get better execution prices because of how this works (why? because retail investors generally don't have new information that will move the price so they are "safe" trades for liquidity providers).
Now robin hood _did_ get fined for "not perform[ing] systematic best execution reviews of several order types". If that's what you were referring to then fine. But if your complaint is just about selling order flow you should better understand what that means. Maybe start with patio11's How Brokerages Make Money[0].
I know this because I wrote an app that connects to Alpaca accounts (as well as other brokerages) to help people build their own custom index funds [0]. It only took a few weeks to build our Alpaca integration, whereas other brokerages often take months/years just to get access to their APIs.
[0] https://getpassiv.com/