The saver tickets are only flexible in the same booking code as your original ticket, so if you bought class X you can only rebook for free if your preferred alternative flight has that class available. As cheap classes get scrapped before departure or only strategically left available on inconvenient flights, it provides a useless scenario. You're indeed best off to just buy a new ticket.
If you want cheap Business travel you buy a saver ticket (if available due to days), if you want flexibility you buy a full flex. The full flex rebook on everything without additional cost for rebooking.