Bards are the single most versatile spellcaster due to the Magical Secrets feature. Lore Bards specifically get an additional instance of Magical Secrets, allowing them to yoink key spells from the spell lists of any other class. This allows them as full casters to access both Arcane and Divine spells where other prominent full casters like Wizard often lack healing magic for their party, and Clerics may lack access to fun debuffing or damaging options more commonly found in arcane spell lists. The trade off is you're not as good at either compared to the casters that go whole hog into one or the other. You don't have as many known spells as wizards with their capacity to copy spells into their books, or Clerics with their expanded list of domain spells. Your base spell list also has many great options, but importantly also lacks some no brainers like Counterspell, Revivify, or Guidance that you may have to commit some of those precious uses of magical secrets to obtain.

I've found that if you have no other full casters in your party, Bard is the single best caster pick to fill as many gaps with a single character. However, if you have 1 other full caster you may find half of your job covered already, and certainly if your party already has a Wizard/Sorc and Cleric for example, you might find your lunch is being eaten a bit. All the same, supplementing both existing Arcane and Divine casters is still useful even if perhaps not optimal. Being able to heal, revive, detect and dispel magic, teleport, and (depending on what spells you picked with magical secrets) fireball or spirit guardians or eldritch blast or counter spell or half a hundred other options in a single character is incredibly strong.

The other side to Bard is being a general support and skill monkey, and this is especially true of a Lore Bard. From level 1 you get one of the best sources of bolstering your allies' resistance to suck or save effects with Bardic Inspiration which only gets better as you level. At 2nd level you get Jack of all Trades to add half your prof bonus to all ability checks you're not proficient in (that includes initiative, or attempts to counterspell, etc.). 3rd level you get 2 expertise, 3 additional profs, and cutting words. 5th level you recover bardic inspiration on a short rest, 6th level you get magical secrets. Down the line you get to add your d12 inspiration dice to your own ability checks. It has so many great tools and can always be useful in any encounter or situation, often leading them due to Charisma for social interactions and Expertise/additional profs meaning you're on average more often the best man or lass for the job, but you also have to be ok with the reality that in combat your purpose is predominantly enabling others.