In physics and science in general researchers use dimensional analysis and they often state that some quantities are dimensionless like for example the number of some objects but I don't think this is true here's why.
Consider a typical problem, a coin has diameter $x\,\textrm m$ and we place a number of coins next to each other in a straight line which has length $y\,\textrm m$, find the number of coins.
The answer is fairly simple we just do $$\frac{y\,\textrm m}{x\,\textrm m}=\frac{y}{x}$$ which looks like it's a dimensionless quantity, but now let's consider the unit $[c]$ that measures the number of coins, so $1 [c]$ means one coin and so on, then $x$ is not measured in meters but in meters per coin, so $$\frac{y\,\textrm m}{x\,\textrm m/[c]}=\frac{y}{x} [c]$$ which is not dimensionless.
The same thing can be done to any problem, we can define a unit of measurement to measure anything.
Is my reasoning correct?
Dimensionality is always with respect to some unit system – and the typical one, SI, does not include "coin" as a unit. Thus if you add "coin" to SI, the number of coins is no longer a dimensionless quantity. However, the SI does include a unit which is very similar to your "coin" unit, in that it merely measures a count of objects, and which some scientists have argued should not be in SI – the mole.
Another example of the relativity of dimension lies in electromagnetism: the constant of proportionality in Coulomb's law has a dimension in SI but is simply $1$ in electrostatic cgs (centimetre/gram/second) and $\frac1{4\pi}$ in Gaussian cgs.
Regardless, there do exist physical quantities that are inherently dimensionless – it is simply not sensible to define a unit from them. The prime example is the fine-structure constant $\alpha\approx\frac1{137}$.