Is shield master 5e a good feat?
Shield master 5e feat would be better than Resilient or Blade Mastery 5e. The only reason I would choose the resilient feat and choose DEX is if I was playing a DEX-based sword and board character. It uses finesse weapons and light armor, as well as a shield. It would (if you add the DEX mod with 1) increase your AC and your Initiative, increase your attack and damage bonus, and make it proficient with DEX saves. You may go for the 5e shield master feat whenever possible. You can’t use the shove thing until you have used your attack/attacks. That can be a great way to benefit your party members, even if you don’t. It will depend on the group. The additional benefit of the Shield Master feat (PHB, page 170) does indeed work against single-target spells. It also works well with Fireball 5e. For a spell-like fireball, the target is the point in space where the ball of fire erupts.

Dex Save for 5e Shield Master feat
You can also use your reaction to avoid taking any damage if you are successful on a dex save if you take only half the damage. Resilient 5e (Dex), which will increase your DEX and give you DEX savings proficiency, will allow you to be more resilient. While proficiency in DEX saves can be a good thing, what else does it offer? Even if you have a Mod increase of 1, heavy armor won’t increase your AC. It will only give you +1 Initiative. Medium armor will only increase your AC if you have a DEX below 14. It won’t affect your strength-based attacks or damage.

I would therefore say that the Shield Master feat is superior in most cases.