Here are some solutions:
1) Limit on the number of new projects : All crypto devs are not greedy. But the problem is that there are so many new projects and so many new developers behind these projects that some people will come out to be greedy from these always.
At such some step should be taken to limit the number of new projects. Only credible people or people with good history should be allowed for this . People can also ensure this by boycotting projects that do not have a solid team.
Limiting the number of new projects is like holding back the growth of the market, cryptocurrencies are a free, open market and they are in the development stage, don't hold it back.
Luna and FTX before bankruptcy, the development team behind are all talented and very good people. So even celebrities cannot guarantee the safety of the project, everything is at risk.
2) Strict punishment for defaulters : Even when coins have collapsed or exchanges were at fault, they were able to get away with all this without any punishments. This is not good as it removes the fear from bad people and they repeat the mistakes in future causing further loss to more people.
Examples should be set in these cases with very strict punishments so that no one can think of duping people of their hard earned money with scam projects in future.
Strict punishment means you accept the government to control us, only the government has the authority to make regulations as well as the power to punish the scammers but regulation will also cost us freedom, privacy.
There is no effective solution, all of this comes from greed, as long as we control greed, we will avoid these scams.