This is high comedy...Thanos is officially a victim of his own success.
In addition to the points Kam made, if you know anything about Eternals you know that they develope certain Eternal abilities to a higher degree than others thru meditation and practice. Thanos utilizes cosmic energy for destructive force far beyond most if not all other Eternals (these can range from a psionic blast of energy as well as blasts of concussive/plasma/cosmic energy from his eyes and hands.
Others have concentrated on matter manipulation, speed, strength, flight etc. So don't believe Thanos can't fly if he wished. It might take a little meditation, might take a lot of meditation, but he'd eventually fly.