In modern politics, and history, a parliament is a legislative body of government.
The purpose of a parliament is to make decisions about what the law says. Something that cannot decide what the law is, is therefore not a parliament. The EU Parliament isn't really a parliament.
> Something that cannot decide what the law is
Good thing the EU parliament decides what the law is, then.
It's not.
> It can only acquiesce to or slow down the Commission's decisions.
That's not all it can do.
To be clear, I’m absolutely not against the European Parliament having legislative powers but that would require the UE to become a federation and we are still far from this.
You're thinking of EU Directives, which have to be transposed into national law by some deadline. EU Regulations (e.g. GDPR) are considered legally enforceable all on their own, though still have a delay.