The opposite of "more uncluttered" can be described as messy, disorganized, or cluttered. These words all suggest a lack of order or cleanliness in a particular space or situation. Another antonym for "more uncluttered" is cluttered, which means that there are a lot of things in the way and make it difficult to find what one is looking for. A third antonym might be "crowded," meaning that there are too many things in an area, making it difficult to move around freely. Opposing the idea of "more uncluttered" also implies the presence of confusion or chaos, suggesting an environment in which things may be difficult to find or navigate.