If you need an online tool to remind yourself of the existence of another person or your plan to interact with them you aren't friends.
Not everyone's brain works the same way. For people with ADHD (and other neurodivergent conditions), executive dysfunction can make it really hard to remember to reach out -- even to people they care about deeply. It's not about not valuing the friendship; it's about how memory and motivation work differently.
Instead of disparaging people for using tools that help them maintain relationships, maybe try having a little empathy -- or at the very least, an open mind. Not everyone connects the way you do, and that doesn't make their friendships any less real.
This kind of tool can be a be useful crutch / prosthetic memory.