The perfect democracy achieving the will of all voters is not achievable, as different groups may promote conflicting policies. There are however parts that are consistent with all populace, and as the cabinets change you definitely can see what they do have in common.

Greek politicians are Greek people too, with same cultural background and overall attitudes prevailing in the society. Ditto for Greek government employees (a huge sector of their economy), who are there to enforce the regulations.

If there is a culture of tax evasion, you can't expect the government to fix it just because there is a tax code in the writing. People's attitude have to change.