As the most prestigious club competition in the whole of Europe, the UEFA Champions League competition isn't a league where any team can relax and feel that they'll be undefeatable probably because they're currently running on a good form because until the final winner of the competition is confirmed, there's every possiblity that the least expected team can surprise everyone and lift the trophy.
Real Madrid are currently one of the best clubs in the competition and are also the competition's most successful club but if they don't continue to play in their current form or probably improve their performance this season, they might not even make it to the semi finals.
Sure, UCL is the highest football competition, all the participants are the strong teams in the world. Real Madrid isn't only a strong team, they also have a good history in UCL. That indicates that Real Madrid deserves to call as the strongest team in the world. But not in each season Real Madrid has an ideal squad, this season Real Madrid squad isn't strong enough without a top striker. Although their current performance looks good, it doesn't guarantee to lead to the semifinal or even the final UCL again.
Real Madrid seems to have become dependent on Bellingham this season, otherwise they will always have difficulty winning matches. Bellingham of course likes to do everything to make his team win the match, but if Real Madrid relies too much on his performance and goal opportunities to win, then I'm sure they will have a very difficult time winning if the opposing team keeps a close guard on Bellingham throughout the match.
Since they have no strong striker, they rely on Bellingham performance. As long as Bellingham can score goals consistently, it won't be a problem. But it is true that sometimes Bellingham gets difficulty to score goals and it makes Real Madrid fails to win the match. I think Real Madrid needs a new top striker in January transfer season.