Now that 1.21.2 has come out and split the food component into two, food and consumable. The consumable component has a field named animation which allows you to specify the animation played when using said item, one of those animations being "block". Currently tho in 1.21.2/3, it only shows the blocking animation in third person but I reported the first person animation missing as a bug (https://bugs.mojang.com/browse/MC-275917) and it has been fixed and the first person animation has been introduced into 24w44a.

Yall should add a option/abandon using the shield as the way of blocking and instead give the swords the new consumable component with the animation of "block" and consume seconds of 3600 (same time as it was hardcoded in 1.8)

bump

Also cool side note, they fixed this bug: https://bugs.mojang.com/browse/MC-152728
This now fixes/reintroduced sprint resetting