TL;DR the ISO standards committees behind SQL are working on bring graph query languages and SQL databases closer together.
Obviously there is work to be done at the storage/query planning layer after that, but I’m hopeful once the surface exists more widely that will drive more work in those areas.
That's not a sufficient argument against adopting SQL for something, but other solutions are certainly _not_ just SQL with extra steps. Not everything maps nicely onto flat tables with predefined slots.
Then there are a few domains that NEED other solutions. In terms of CPU cycles these may be consuming more resources. These are operating systems, game engines, ML libraries, search engines, social media platforms and huge webshops like Amazon.
But to store all data in Spark or MongoDB just because that's what <insert Cargo Cult idol> is doing makes about as much sense at programming everything in C/C++.