Many people go on about the RAF being on its knees but forget that the Luftwaffe was spent. It had lost a huge amount of trained and experienced aircrew, planes were suffering from reliability problems along with lack of spares, crew morale was low.
The RAF had four air groups defending the UK only one of which was fully engaged, the other three rotated Squadrons with 11 Group (which defended the South East). RAF fighter strength was greater at the end of the BoB than when it started as was bomber and coastal command (luftwaffe strength was roughly what it was at the start but a higher percentage was unservicable). The Empire Air training Schools were providing increasing numbers of pilots so aircrew strength was also starting to increase.
At the very worst case scenario 11 group could have been pulled back to beyond German fighter range and still be able to hit the bombers.
Never mind the simple fact that the Kreigsmarine could not do its required job and they had no real way of transporting the troops across the Channel.
It was easier for the other services to blame the Luftwaffe than to admit none of them could actually fullfill their obligations for Sealion.