Bless is extremely powerful and don't let anyone tell you otherwise. It's an average of a +2 on all attack rolls and saves for three people or more. It's one of the best spells in the game and it makes the cleric class a potent choice to play. I wouldn't take it away or modify it because it is one of the most powerful of the cleric's spells and it would be like taking away shield from an arcane caster or eldtritch blast from a warlock. It may not fit every situation. It is an extremely cheap resource for boosting battles often.
Each of the caster classes have a few uniquely effective and potent spells. It's those spells that allow that particular caster (and bards if they so choose) stand out. I wouldn't take them away or modify them. Just let the players have their fun with the abilities and toughen up the enemies. It's the enemies that are too weak in 5E, not spells like bless that are broken or too strong. Enemies need to be buffed up to suit your table's style of play. Have fun making stronger enemies that can challenge players using spells, special abilities, feats, and magic items. Monster creation has never been so easy and enjoyable. I've been making tons of creatures to challenge my players and having a blast doing it.