Postgres was relational for the first decade of its life, until the infamous '95 release when it sold its soul to the devil. You could dig up on old version, perhaps. But, yes, the tradeoff for real-world use was already mentioned.
The relational model is superior as complexity grows (although arguably the deductive model is even better), but the tablational model is superior for simple line-of-business stuff, so pick your poison. Like with all things engineering, there is never one perfect solution that satisfies everything. If, like the earlier comment suggested, you keep your SQL simple then you'll be fine.
I understand that SQL is pseudo-relational, but it’s as good as you’re going to get if you want something you can use for actual workloads.
0: https://reldb.org