Radio Transmissions and their Effectiveness

For over 8 decades humans have been sending radio signals into space, intentionally and unintentionally. Though this has only a limited effectiveness, because if aliens DO hear you, they will be hearing sounds and broadcasts that might be ancient by that time. Also, how do we know that aliens are not TOO ADVANCED to hear us? We have not discovered many transmissions, though we might be able to intercept a very old civilization's calls with radio waves. If we do contact an alien civilization, it would take many thousands of years to intercept their message, which we might not even be able to decode or understand. There is much uncertainty with radio transmissions.