Ferrari has had the same problem (since 2009). Can't develop a car in season to save their lives. They were blown away by Red Bull/ McLaren during in season development and the same since Merc domination. They outperformed in those years given the cars they had. The real problem is year after year the designers, engineers etc are not good enough, but no one will talk about that.
Ferrari was just as far ahead of everybody this last race as they've been most all season. It's just Mercedes have kicked it up an extra gear we didn't realize they had. Merc had clearly been underperforming in a number of cases beforehand. Ferrari is still far and away ahead of even Red Bull. So it's not like we're falling back due to poor development. Our car just isn't as good as the Merc on a fundamental level. We might be able to challenge here and there in specific situations that really suit us, but I think expecting we can fight toe-to-toe for the rest of the season is pretty much over, at least for me. We couldn't tell much at Montreal due to circumstances, and Baku *could* have been a one-off, but Silverstone is pretty good evidence that Merc really have just put things together.