I am not entirely sure why WordPress’s basic button design is so bad, but fortunately, it is easy enough to change. If you are like me and get tired of adding a class to every button, you can just add this CSS snippet to align the default button with ACSS. Adjust as needed.

.wp-block-button__link {
    background: var(--primary);
    color: var(--white);
    padding-block: var(--btn-padding-block);
    padding-inline: var(--btn-padding-inline);
    min-inline-size: var(--btn-min-width);
    line-height: var(--btn-line-height);
    font-size: var(--btn-font-size, var(--text-m));
    font-weight: var(--btn-font-weight);
    font-style: var(--btn-font-style);
    text-transform: var(--btn-text-transform);
    letter-spacing: var(--btn-letter-spacing);
    text-decoration: var(--btn-text-decoration);
    border-width: var(--btn-border-width);
    border-style: var(--btn-border-style);
    border-radius: var(--btn-radius);
    border-color: var(--btn-border-color);
    transition: var(--btn-transition, var(--transition));
    justify-content: var(--btn-justify-content, center);
    text-align: var(--btn-text-align, center);
  margin-block:var(--content-gap);
  &:hover{
    background: var(--primary-hover);
    color:var(--white);
  }}
CSS

If you are actively using the ACSS global styles panel, you can use 

.wp-element-button{

  @include btn('primary')

}
CSS