-ctd-
ii. Alien civilisational development. - I think its a sweeping generalisation to automatically assume that there must self evidently be older, wiser, more technologically advanced civilisations out there. And its also a stretch to conclude that such civilisations would necessarily be interested in ours. For such a society to have any interest in ours, there has to be a reason for the interest - trade, politics, food, filial affection, something - which would mean they have to be similar to us, which implies a similar planet as well as a similar evolutionary and cultural trajectory - Multiply these extremely rare factorials together and the likelihood of a reasonably close civilisation old enough and advanced enough to visit the Earth becomes smaller and smaller.
iii. Galactic Scale. How did they find us in the first place? The mind-melting enormous number of Galaxies,Stars and Planets within the Universe have made us a minute target, one effectively invisible for 99.99% of humanities existence, until around 80 years ago when we first started broadcasting radio and and then TV signals - so our "Digital Footprint" has only radiated out around 80 Light Years at best.
You could, I suppose, speculate that the alien civilisation would have no need to find us since they seeded the earth in the first place, but thats all it is - speculation, with nothing in evolutionary theory, DNA, molecular biology or the fossilb record to support it at all.
So, to conclude - yes, I believe that alien civilisations are probably out there - but even given the vastness of the universe and the even more mind boggling number of galaxies, suns and planets that are out there, I don't think it credible that they have ever visited us.