They have been effective for millenia, even before democracy. The only thing ineffective now is people saying so. With all the evidence in the world that protest works, people bizarrely disarm themselves.
The targets of the protests take great pains to convince you of it; that should tell you something. They'll bluff until they lose.
It has been ineffective. We've seen peaceful protestors smeared, and beaten and harassed by the police. We've seen counter terror laws abused to smear and arrest leaders. We've seen clampdowns on what protests are allowed to go ahead, and at least on the UK they are pushing and pushing for "tougher" laws to crush protests.
It's only ineffective if your measure is immediate, complete victory. You don't win everything, you face defeat, and you quit? Then I agree, your protest is useless. You think you are somehow entitled to results? Yes, your protest is worthless, a pantomime. Protest isn't a ritual you perform - a raindance that you do - and then the gods respond with whatever it is you asked for. Protest compels results - it's embracing that you are the agent, you are the power, you make it happen; the enemy will give you nothing. If you don't understand that, if you aren't planning for it, if you have no strategy that will compel victory, then you're just entitled. (I think the latter is the problem with most of the protests now - they're doing raindances.)
And you go around telling people how hopeless it is? Have you ever accomplished anything? Has anyone who has ever said those things? People saying those things are the first problem - if they were on my team, I'd tell them to never say that again or simply don't come back.
Regardless, the protests have altered behavior, including by European leaders and by the most powerful person in the world (POTUS) and a candidate for that office (Harris). They may cost Harris the election by denying her enough votes in Michigan. And though nobody can say for sure, they arguably have altered the Israeli government's behavior, though the protestors will certainly and understandably say, not nearly enough.
Finally, to evaluate protest, compare it to the alternative: silence. Imagine horrors went on and society responded with silence. Imagine how demoralizing that would be to the ordinary person, who does have a moral conscience. Imagine how crushing to public morality if nobody said anything. Protestors are essential.
[0] There was some research, I think from 10-20 years ago, that showed that it succeeds at a high rate. But I don't recall what kind of protest, etc., so I hope someone else knows about it.
We still have no meaningful movement on climate change, an antidemocratic political system, no social safety net, Palestine, etc.
Can you give any examples?
You haven't achieved more because you and all these other people quit. Of course you're not achieving anything.