A dedicated IP isolates reputation entirely to one sender's own behavior, unlike a shared IP pool where reputation reflects every tenant using it. It requires its own warm-up ramp regardless of how established the sending domain already is, since IP and domain reputation are tracked separately.
Dedicated IPs make the most sense at meaningful, consistent volume; at low or irregular volume, a shared pool with good reputation management often outperforms an under-warmed dedicated IP that mailbox providers have too little history on to trust.
A dedicated IP does not replace domain-level authentication (SPF/DKIM/DMARC) or list hygiene; a dedicated IP with a poorly maintained list still degrades, it just degrades in isolation from other senders.