There's a difference between "an engineer" and "a good engineer".

So those saying he's not an engineer at all are probably wrong, but those saying he's a good engineer probably aren't correct either.

I think it's also the case where his misses are more evident. If you said "We'll get to Mars in 10 years", people will likely have forgotten you said that after 5 years, much less 2 years after your boasted time frame expires. So people credit you for big ideas while not having to deliver on anything. Every year, we've been about a year away from fully autonomous self-driving cars.

Complaining about twitter and saying how you'd fix it is easy when you don't control twitter. But actually fixing it is a different story once you have all the control.

Promises are easy to make, harder to deliver.