Each situation is different but the commonly brought up drawbacks for Romania are lack of familiarity, lack of precedence, language, bureaucracy, corruption, poor banking, difficulties attracting foreign talent, and the local currency being rather useless.
In every situation, jurisdictions like Malta, Cyprus, and Ireland (and non-EU alternatives) have been more attractive choices.
The 3% tax on revenue is great if you're small business with small ambitions. If you grow your business to above 1 million EUR turnover, the tax burden shifts to 16% on profits, which is still quite low but higher︀ than for example Malta, Cyprus, and Ireland which are far more popular jurisdictions in most︁ other regards.