I agree with you; the biggest surprises of the tournament so far have been in Group E. If Belgium suffers another defeat, they may not be eliminated because they can still qualify out of the group as the third-placed team. However, this situation would make their job harder. Considering today’s performances, it is possible that Ukraine will finish last in the group, and Belgium will end up third.
This is just their first game and I think it is way too early to judge them base on this performance today alone, The game is still open and Belgium can still come out top in their group if they win all their remaining matches from here despite that they lost in today's game but the correction may come in their games ahead, and I still doubt Belgium won't qualify for next stage of this competition.
Overall Belgium game today was no better than Slovakia and of course this is beyond our expectations, at first I thought Belgium would play impressively because they were playing with the main squad moreover, I still remember how they played in qualifying but unfortunately today Belgium lost. I agree with you, Belgium is not over yet they still have a chance and I can see Belgium being in an easy group yeah at least they can take a place as runners up in group E as long as they don't repeat the same mistakes.
By the way Belgium still has 2 matches ahead against Romania on June 23 and Ukraine on June 26 so Belgium must win these 2 matches if they want to secure the next round and if they only win once then they are not safe, between these two matches, against Romania it is an important match because if Romania win then they will definitely be safe by collecting 6 points.