In addition to the solution of Amit above, this is only for the category page. To change it on the homepage i did the following too:

Goto

app/design/frontend/{ThemeVendorname}/{Themename}/{ThemeVendorname}_ProductWidget/templates/product/widget/content/list.phtml

Somewere in line 173 you see this code:

<button data-mage-init='{"redirectUrl":{"url":"<?php /* @escapeNotVerified */ echo $block->getAddToCartUrl($_item) ?>"}}'
                 type="button"
                 title="<?php echo $block->escapeHtml(__('Add to Cart')); ?>"
                 class="action tocart btn btn-default btn-cart">
                <span><?php /* @escapeNotVerified */ echo __('Add to Cart') ?></span>
               </button>

Change this code with

<a href="<?php /* @escapeNotVerified */ echo $_item->getProductUrl() ?>" title="<?php echo __('View Product') ?>" class="btn btn-default"><?php echo __('View Product') ?></a>

Go to line 184 and see this code

<button data-post='<?php /* @escapeNotVerified */ echo $postData; ?>'
                 type="button"
                 title="<?php echo $block->escapeHtml(__('Add to Cart')); ?>"
                 class="action tocart btn btn-default btn-cart">
                <span><?php /* @escapeNotVerified */ echo __('Add to Cart') ?></span>
               </button>

And change also this code with

<a href="<?php /* @escapeNotVerified */ echo $_item->getProductUrl() ?>" title="<?php echo __('View Product') ?>" class="btn btn-default"><?php echo __('View Product') ?></a>

Hope it helped somebody else too!

In addition to the solution of Amit above, this is only for the category page. To change it on the homepage i did the following too:

Goto

app/design/frontend/{ThemeVendorname}/{Themename}/{ThemeVendorname}_ProductWidget/templates/product/widget/content/list.phtml

Somewere in line 173 you see this code:

<button data-mage-init='{"redirectUrl":{"url":"<?php /* @escapeNotVerified */ echo $block->getAddToCartUrl($_item) ?>"}}'
                 type="button"
                 title="<?php echo $block->escapeHtml(__('Add to Cart')); ?>"
                 class="action tocart btn btn-default btn-cart">
                <span><?php /* @escapeNotVerified */ echo __('Add to Cart') ?></span>
               </button>

Change this code with

<a href="<?php /* @escapeNotVerified */ echo $_item->getProductUrl() ?>" title="<?php echo __('View Product') ?>" class="btn btn-default"><?php echo __('View Product') ?></a>

Go to line 184 and see this code

<button data-post='<?php /* @escapeNotVerified */ echo $postData; ?>'
                 type="button"
                 title="<?php echo $block->escapeHtml(__('Add to Cart')); ?>"
                 class="action tocart btn btn-default btn-cart">
                <span><?php /* @escapeNotVerified */ echo __('Add to Cart') ?></span>
               </button>

And change also this code with

<a href="<?php /* @escapeNotVerified */ echo $_item->getProductUrl() ?>" title="<?php echo __('View Product') ?>" class="btn btn-default"><?php echo __('View Product') ?></a>

Maybe you have to style the generated URL with CSS. Hope it helped somebody else too!