Do DIY eCommerce platforms start to break once sales get real?

Seen a bunch of small shops using drag-and-drop builders like Shopify or Wix. At first glance, everything looks fine. But once traffic or product count grows, issues start popping up. Slow loading, mobile bugs, plugins clashing, SEO dead weight.

These platforms pitch “easy setup”... but when things get serious, they feel kinda fragile.

What’s been the biggest struggle you've had running an eCommerce store on one of these platforms?

Did you ever reach a point where rebuilding felt easier than fixing?