Why is Belgium (and Luxembourg, Switzerland, Austria, Norway) still above consumption CO2 levels per capita of 1990? While many others did go down
My answer will not be complete, but consider one factor: population.
Belgium population per year:
1990    9,967,000
2000    10,251,000 (+10.2%)
2009    10,796,000 (+5.3%)
2018    11,376,070 (+5.4%)
On top of that, you are considering countries with relatively small population increasing significantly (Belgium, Austria, the Netherlands). Most of the population increase is from immigration and high fertility rate of the new population (see the CO2eq impact of about 9tons per capita on the parents due to a new born), with industrial powerhouses like Germany and Italy where a lot of the production has been delocalized in the same time period (check CO2 of Romania or Spain)