Is MERN good for SaaS development?

Yes. MERN is one of the strongest choices for SaaS today because the full-stack JavaScript architecture lets one team move across every layer without handoff overhead. MongoDB's document model handles the flexible schemas SaaS products require during early growth. Node.js handles concurrent tenant connections efficiently. React with Next.js covers both the marketing site and the authenticated application in one codebase. At Acquaint Softtech we have shipped 40+ MERN SaaS products since 2013, across EdTech, FinTech, B2B, and marketplace verticals.