I feel like aikido is a great “second art” if being used for self defense.
The techniques are sound. I’ve used wrist locks in real life situations. The results have been great. Note, I did not train aikido, but learned the techniques I know as they were classified in another art as aikijujutsu.
Part of the issue is you can’t train worst locks live. A full speed wrist lock can be devastating, and wrists don’t heal well. However the training is too soft, though I feel this is part of the reason.
The other part is that aikido had removed the atemi waza (striking) that was in the aikijujutsu training. In most situations, you need that to set up a wrist lock. It’s even talked about in Angry White Pyjamas.
So, aikido can be a good are if you already have a good understanding of violence. If you are coming from a live training background, it’s easy to slow down. However, only learning aikido will not teach you how to speed up for a real fight.