The way I see it is this...
There are loads of things we can do to beat Covid - not just the app, but wearing a face covering in public, maintaining social distance, washing / sanitizing hands regularly, avoiding crowded places, limiting social interaction, avoiding public transport if it's not essential, isolating ourselves if we have symptoms, and cutting right back on those things that, in the general scheme of things, aren't truly necessary to live a good life.
They all help. But we are all different, as are our lives. The app is only one tool in a very big box of tools, and, if like me for instance, you're in a situation where is isn't the right tool for the job, you use one that's more appropriate.