Opponents are as easy to find as opinions. Neither are worthy commodities since they come in over-abundance. No matter who you are or what you do, however good or bad, someone will always tell you you’re right and someone else will always tell you you’re wrong.
Knowing which voices to heed and which to ignore comes from proof; harken to people who have done and proven that their ideas actually work.
But, that “proof of competence” test should come earlier. First, choose your destination wisely, then heed the voices who want you to get there. They are your true constituency.