1. Lack of a zero digit: The Roman numeral system did not have a symbol for zero, which made it difficult to represent large numbers. For example, the number 1000 had to be written as "M", while 1001 had to be written as "MI".
2. No place value: Roman numerals did not use place value, which meant the position of a digit did not affect its value. For example, the number XXXIII could represent 33, but it could also represent 2023 if it was written as "MMXXIII". This made it difficult to perform arithmetic operations, as numbers had to be converted to an abacus or other counting tool to be added or multiplied.
3. Inconsistent subtractive principle: The Roman numeral system used subtractive notation to represent numbers less than 10, 100, 500, etc., but the rules were not consistent. Only specific digits (I, X, C) could be subtracted, and the number being subtracted had to be immediately to the left of the number it was subtracting. This made it difficult to remember and apply the rules.
4. Inconsistent use of symbols: Roman numerals used different symbols for different multiples of 10. For example, 10 was represented as "X", 100 as "C", and 1000 as "M". This made it difficult to understand and use the system consistently.