I ran a survey asking Dungeons & Dragon’s players to rank the feats of 5th Edition into tiers (broken, great, good, average, bad, junk).
The feats are generally well-balanced. Aside from three usual suspects, no other feat was voted broken. On the other end of the spectrum, only four feats were voted bad (2) or junk (2). The other 50 of the 57 feats were all voted great (10), good (22), or average (18).
Xanathar’s Guide to Everything Feats
It appears the developers did an even better job of balancing the racial feats presented in Xanathar’s Guide to Everything. No feats were registered as broken, bad, or junk. Only two feats were registered as great. Only one feat was registered as average. The design team did a great job balancing the majority of the racial feats to “good”.
Admittedly, Elven Accuracy (great) is teetering towards broken:
However, Prodigy (great/good) recorded the same number of votes for great and good, and thus could be placed into the good tier with the remaining feats:
Things DMs Nerf or Ban
Among the Tier 1 Feats, we find the usual suspects: Lucky (allowing you to reroll dice 3x/long rest), and Sharpshooter/Great Weapon Master (-5 to Hit/+10 Damage).
The developers have admitted that the Lucky feat is “maybe too good,” due in part to its interaction with disadvantage to cause “super advantage.” While you can homebrew around this, the official stance is to let your players pick from three dice.
With respect to Sharpshooter and Great Weapon Master, the primary gripe is the -5 Attack/+10 Damage mechanic. The problem is that it becomes advantageous to use this ability every round, resulting in an feat that enables characters to vastly outdamage their peers, without being restricted to situational usefulness. Various fixes have been suggested to nerf these feats, including: separating them from the other features provided by the feat, tying the -attack/+damage modifier to proficiency, setting level requirements, or just an outright ban.