The one that jumps out at me is Knock. Given it's downside (which is a pretty big downside), making it also cost a spell slot is unnecessary. I'd be okay with removing the downside when cast with a spell slot, because that's a daily resource (as opposed to a skill check that requires proficiency).
Magic Circle seems like it should also be a ritual. The purpose is to set up a summoning spell, so taking up an additional slot seems unnecessary.
Magnificent Mansion is also pretty hefty for a 7th level spell slot, considering there are lower level options that are rituals that provide almost as good an option.
Given the casting time and use for travel (albeit planar travel), Astral Projection seems like it might also be better as a ritual. That way the caster still has access to their precious 9th level slot while providing the key to reach an adventure.
Anything that summons should definitely NOT be a ritual. This includes the find steed spells and planar ally, because otherwise the party could have an infinite supply of disposable allies. I don't like that find familiar is a ritual for this very reason.