It worse than GBA obviously, but also worse than Color and I would assume Game Boy Pocket. Buttons and ergonomics are closer to SP, which should say enough. And if one game has a huge and obvious error, more do. There will likely be tons of errors that aren't fixed, these are big libraries. If you want the best possible option for handheld, this is not it. Personally I'd also point out that while the screen is nice, it's too big to be authentic.This is literally the first thing I've heard of buttons being worse. The ergonomics won't be worse than anything other than possibly a Game Boy Advance. And modded screens (while a huge improvement over original screens) are hugely worse than the screens here. Mod screens are ultimately not designed for Game Boys and have perceptible display errors.
The errors with the Pocket will be fixed (the power of FPGA). I don't get why you're so against this. It's a great product, and if people can afford it and they want it then they should feel confident getting one. Personally I won't, I have all of the previously mentioned stuff and a MiSTer. But "get an Anbernic" or "mod a Game Boy" is nuts if people want the best possible option with minimum faff.
Do you not have one?