Cleric is a lot like Wizard with even worse issues in some ways.
It's main thing is knowing like, a huge number of different spells and being able to cast them quite a lot. For reasons of tradition and in order to excuse it having class features, most of those spells not cool stuff for the Cleric to do, but things to help other people.
It has some class features, at least, but there's not a huge amount to work with.
And as
@James Gasik points out, they're expect to hold back on a significant proportion of spell slots to help the rest of the party, healing, curing, etc. etc.
In 4E, when they were put into the AEDU structure, and their main heals were a thing all "Leader" role characters could do, they became a vastly more dramatic and dynamic class, with a ton of AEDU spells that just don't have close equivalents in 3E or 5E. Even some with the same names worked in much more dramatic ways. There was also far less expectation of holding spells back thanks to them being a Ritual Magic class and/or spells not being Daily.
I feel like we could stand, if making dramatic changes, to make the baseline Cleric a worse caster, maybe 2/3rds caster or some other structure that isn't Full Caster, and give it a lot more in the way of abilities. But I don't think we'll see anything like that. In fact I suspect we'll see no major changes to Cleric, because people who are okay with it, play it, and people who aren't, play Bard or Druid or the like.