I would agree that ADRs are not really necessary if you work alone. Maybe not even within a team if it stable over a long time.
Where ADRs are helpful is when many teams cooperate and if people come and go. The reviews happen implicitly because the decision is discussed among many people.
I'm not sure. I work in a small stable team and I had to do a tech due diligence report... it's really amazing being able to go two years into the past and pull the exact reasons why certain design decisions were made.
Not all our designs and decisions panned out ofc, but just having the articles already helped a ton getting through that DD and it really helps give new starts a much better feeling for the code base and where it came from
Where ADRs are helpful is when many teams cooperate and if people come and go. The reviews happen implicitly because the decision is discussed among many people.