Redirecting 18k pages to the homepage is risky for SEO. While it might seem like an easy fix, it could dilute the homepage's authority and negatively impact user experience. Instead, a more targeted approach is ideal:
Category-Based Redirects: Redirect related content sections to the most relevant category or subpage rather than the homepage. This helps preserve relevancy and SEO value.
Custom 404 with Helpful Links: If category-based redirects aren’t possible, a custom 404 page with links to important sections is a good option. This minimizes user frustration and preserves SEO value without overwhelming your homepage.
Overall, avoid overloading the homepage with unrelated redirects to prevent potential penalties or ranking issues. Aim for logical, content-driven redirects where possible.