It may already have been said above, but my impression is that most of the outspoken disrespect for aikido comes from people who do not practice any martial art at all. That makes them very sure of which one is the best, and which one the worst.
For example, when I check the channels of those who write the most rude and dead-certain comments on my YouTube aikido videos, they never have any martial arts videos of their own.
People who actually practice have a much more nuanced and ambiguous view on it all.
I have been fortunate to meet many very prominent practitioners of other martial arts, and I found none of them hateful toward aikido. Quite the contrary.