Hello — I'm Nick Healey
I've been designing award-winning, people-pleasing, industry-changing tech products for over 25 years.
The "Last Responsible Moment" is very early indeed for Product Design decisions.
(In Code Design, not so much.)
So if you'd like Agile projects to be more predictable and the products easier to use, start with an "Architect" – from a downward-thinking CPO to an upward-thinking interaction designer.
And before you code, let them think about and analyse what users would really like/need, and draw up some system-wide wireframes that deliver on that (just like an Architect's blueprints), but only designing just deep enough to show that an overall design hangs together, and that all the key things you want your users to do will indeed work, clearly and simply.
This is entirely Agile-compatible, and will help your Agile software teams deliver you software first time that does what your users want, in ways they can understand, remember, enjoy, even love.
Below, some examples of what I know, and designs I've architected. Some of these designs have changed industries, because they work first time, "out-of-the-box", for ordinary people.