タイトルは可変して、ボタンは下揃え（flex）

.blog-waku {
display: flex;
justify-content: space-between;
flex-wrap: wrap;
}

.blog {
display: flex;
flex-direction: column;
border: 1px solid #8FC3EA;
width: 48%;
box-sizing: border-box;
padding: 30px;
}

.blog .contents {
margin-top: auto;
}

.blog:nth-child(odd) {
margin-right: 2%;
margin-bottom: 4%;
}

.blog:nth-child(even) {
margin-left: 2%;
margin-bottom: 4%;
}

■flex-wrap: wrap;
折り返す

■参考サイト
https://taneppa.net/flexbox_btn01/