Lead marketplaces like Angi sell you access to homeowners who are often talking to three, four, or five other contractors at the same time - you're paying for the introduction, then still competing on the same speed-to-reply and presentation factors covered elsewhere on this site, except now you're also paying per lead whether or not it closes.
Owning your own system - a website that ranks, a Google Business Profile that converts, and automated follow-up - costs more upfront but has a fundamentally different economics curve. The marginal cost of an additional lead trends toward zero as your organic presence builds, versus staying flat or rising with a lead marketplace.
The practical answer for most remodelers isn't "never use Angi," it's "don't rely on it exclusively." Use marketplace leads to fill gaps while your own system builds, then let organic and referral leads - which convert better and cost less over time - take over as the dominant source.