So elected MEPs have to go cap in hand to a bunch of unelected commissioners who then use their discretion to decide whether or not to act on that to propose legislation?
I don't know who else is asking the Commission to propose legislation along with MEPs, but neither do you, or anyone else. That's precisely part of the problem.
Do you really not see how this attenuates democratic representation of electorates? It's like having an elected House of Lords but a permanent House of Parliament, composed of appointees who you can't get rid of if they propose legislation you don't like.
The power to get rid of politicians if they piss off the electorate is a huge one, and we shouldn't take it for granted. Think of all those Tory U-turns lately. Tax credits. PIP cuts. Forced academisation in schools. All of which have come about because the politicians in question know they are voted in, and can be voted out again, so they just can't push changes through that piss too many people off.
Weaken that power, remove the fear of being voted out, and you start to see decisions forced through with total indifference to public outrage. After all, if the public can't vote the decision-makers out, who cares what they think? Think of what's been done to Greece, the forced privatisations and butchering of the welfare state there and you start to see what happens when unelected technocrats are in ultimate charge of political decision-making, with no fear of reprisals from an angry electorate.
This, fundamentally, is why we need to cling to UK parliamentary sovereignty and resist the attempts of bureaucrats to whittle it away under the guise of 'labour protections' or economic scaremongering. UK parliamentary sovereignty could be used to push through the right-wing will of the people, but also the left-wing will of the people. The key point is that it's the will of the people. Remove the accountability of politicians to the people, and they just do what they think is best - and if the people don't agree, tough.