It's seasonal, but there are ways to make it a profitable season full stop. Just needs the right routes and scheduled aircraft on them.
So why do so many/nearly all airlines fail to make a profit over these months? Making money in specific months/seasons is not a trend curious to just the airline industry either.
You're right, there are certain routes/network changes that can be made. Reducing aircraft utilisation is even an option. Most airlines (and certainly Easyjet) impliment these changes. However, they are done primarily to reduce losses.
I'm not going to patronise you. You know that there is huge seasonality in the industry and by virtue it is difficult to make money in the low months but very easy to make money in the high season. Consequently, what do you think Easyjet does wrong in the Winter that suddenly corrects itself in the Summer?
As for Stelios. I don't always agree with everything Easyjet does believe me. However, this guy really needs to shut up or sell. Growth has been measured in my opinion unlike FR's huge commitment to Boeings. Don't get me wrong, there have been issues along the way such as LGW's appalling OTP/Operational Performance last Summer but this wasn't down to the growth rate of the airline.