I disagree. Did Spurs built on the foundations he put? Did Chelsea? Those two successful examples (Juve and Inter) had a director who knew what he was doing. Not that I don't want his appointment, because it at least gives you a shot of being a team. But with this current management I won't put money on success post Conte.
I'd agree, the majority of the build comes from the Director. He is the one responsible for long term planning of the team.
Conte will always be focussed on immediate success. Transfers like requesting Lukaku show that. He is a useful player for a season or 2 but he is at the latter part of his career, his value will be going down and he will need replaced in a couple of seasons.
But what Conte does bring is a change in mentality. He creates an environment which is competitive, players who don't work will not be tolerated and usually a winning mentality. For long term success, Conte and a good Director is an excellent combination. But that change in mentality can't be understated and something this club badly needs.
The potential problem you have is if Conte wants short term targets and the Director looks to build for longer.