Pact Of the Tome is kinda based on Ritual Tome of 4e. The idea was anyone could learn ritual magic tied to key skills - usually Arcana, Religion, or Nature - that encompassed out of combat abilities. So, a warlock or a sorcerer was just as good at arcane rituals as a wizard. Virtually all of the AEDU were combat oriented; even the utility were primarily non-direct damage or direct healing combat options.
Anyways, we move to 5e. Wizard, rather than being defined by implements like in 4e, jumped back to being the Spellbook Class. It kinda swallowed rituals as one of its main gigs as a result. Right now, the old Tome effectively lets you become a bit more "Wizard-like." Which is different enough from Blade pact - you do become more Fighter-like, but only in that you become part-martial. Tome is very specifically more Wizard-like instead of more full-caster-like.
Maybe its time to drop the rituals entirely, let them be Wizard's schtick, and focus more on just the cantrips? Warlock is supposed to be the cantrip caster. Why not just offer more cantrips, but let them do more and be more interesting? Let Agonizing/Repelling/etc apply to all cantrips. Let Minor Illusion, Message and Prestigitation, which have limits on the number of instances of simultaneous casts active at once, have more active.
This would definitely feel more warlock-y, push the feeling of being even more of a caster than base warlock.
Alternatively, you can go more of a book-of-contracts vibe. Where you get benefits from people who sign their name in the book. For a price. Or something.