FitzTheRuke
Legend
All the Conjure spells, as well as animate object, need to not allow 8+ creatures. That slows the game down way too much. One summon is enough.
And they have been more or less replaced with Summon spells now, so just remove them.
This more has to do with 5e monster design, really. I mean, I haven't understood for years why they don't use the perfectly good Swarm mechanic used in 3e and 4e. It exists in 5e, but it's been marginalized down to a couple of types of vermin.
It was used more effectively in 4e, but even then - the community used it more than the designers. I remember using a gargantuan horde of ogres (single stat-block representing a shedload of ogres) as a high-level threat.
Frankly, a DM should never have to deal with more than 4-6 monster stat-blocks, and a player should never have to deal with more than two. (Their character and something they summon, or a pet). BUT... that doesn't mean that there can't be more creatures involved in the game's story. "Swarm" rules (better called "Hordes" IMO, to avoid them being reserved for vermin).