Open source softwares can be good, but they don’t have a company’s brand on the line if their quality control is poor.
All simulation softwares are tools. Like a hammer, a lot can be done with it, but it depends entirely on you skill. That beings said, simulation softwares are about as complex a tool as it gets. What may seem like getting “the right answer” may very well just be creating nice pictures without a fundamental understanding of the physics and the solution scheme of the software.
What anyone getting started with simulation needs is the right mentor more than the right tool. Do you have someone that can review your work, who is highly skilled?
For full disclosure, I do simulation and analysis for a living so I am biased. I do technical support for FEA and CFD softwares and have seen so many invalid analyses that it makes me a little jaded sometimes.
I can answer more specifics if you have them.