There will be plenty of earth-like planets, most likely with earth-like creatures possessing earth-like DNA? Why not?
The only evidence we have that's "most likely" is because that's all we've observed. Black swans are real.
Anyway, we're not so far from creating self-replicating AI technology that's going to inevitably work out that we're it's biggest threat. Our best hope if we encounter alien "life" before we expire as a species is that it might enjoy keeping some of us as pets or zoo exhibits. If that life is organic, we'll probably be food - doomed unless they run a quota management system on the resource.