I have read of many alternatives, though RPi has one feature, nothing can beat it today - community support.

99% problems you'll see on your RPi, you can find a solution to them in 5 minutes with Google.

Maybe it will sound like nitpicking and also RPi has versatility and extensibility for rapid development. Want add camera? No problem. Connect to screen? No problem. Few USB devices? No problem. GPIO control? No problem.

Probably it's just a rant with possibly very long discussion, but if you do not know what crazy or fun thing you going to do tomorrow, RPi probably got your covered, whereas others - not so much. So if RPi (let's say the 'normal' one, not the Zero) had builtin WiFi and BT, personally I would be covered in any way I need and would not need any dongles at all.