When I first joined the Android beta Robinhood had a very clear message before every purchase: "to protect the user from volatility, Robinhood creates market orders as limit orders with a 5% higher price". So, yeah, that means that if you place your market order at $100, they reserve the right to broker it all the way to $105, which is bullshit. On average it won't be that high, but still, if you were planning to make a 0.5% profit, you'll always lose.
The only way to get around that is by creating a proper limit order yourself, setting the price a couple cents the current price (to match the BP you are willing to give up.)
Since I started doing that, things became way more predictable.
Let me clarify my position:
I think most people should invest.
And part of that investment should be in the stock market (how big a part depends on their individual age and risk tolerance).
And for most people, the only stocks they should ever buy are ETFs that are passively managed with low fees.
Yes they need to do enough research in as far as to find out that they should only be buying ETFs (and that kind of research does not require any kind of support from their brokerage). But they shouldn't be tempted to do more specific "research" to pick their own stocks because most people who do that are doomed to underperform the market anyways.
So in the end, the fact that Robinhood lacks a decent research platform shouldn't matter to most regular investors because they should only ever buy specific ETFs anyways.