Interesting chat with my son recently who runs the machine shop in a major composite manufactures supplying the F1 industry.
Amongst their regular clients are Red Bull, Mercedes, Toyota (WEC) etc, so he gets to see many of the new car parts long before anyone else.
They recently had a Williams chassis in for machining, as Williams own big CNC rig was down. "Looks like the same chassis they had 10 years ago" he said somewhat surprised. The front running teams have moved the game on significantly in the last few years.
Without the constant investment in facilities, people and infrastructure it should come as no surprise that there is a gap between the leading 3 teams and the rest.
Even if you do have the investment (Renault?) there is no guarantee that you can bridge the gap without a continuity of all the factors that make great teams.
Obviously, funding plays a major role, but catching up on a decade of under investment, and then beating those fortunate to have that resource is going to be a mountain to climb.