Is it worth learning Data Structures & Algorithms for web development?

Some, yes. Not for the trees themselves, but for the reasoning they teach:

Directly useful day to day: - Big-O intuition: recognizing that users.filter(u => admins.includes(u.id)) is O(n×m), and that a Set makes it O(n+m). This is the #1 source of "why is this page slow with real data". - Hash maps and sets for lookups and deduplication, queues for jobs, trees for nested comments and menus, graphs for dependencies and permissions. - Understanding how database indexes work (B-trees) and why pagination with OFFSET gets slow.

Mostly for interviews: dynamic programming, advanced graph algorithms, tricky puzzles. Worth practicing if you target companies that interview that way (big tech often does, many startups don't).

Practical approach: learn the core structures and Big-O well (a few weeks), then study interview-style DSA only when you're preparing for interviews that use it.