How to import content to Drupal 8 site by inserting it directly in the database?
Turned out that I also had to update node_revision table, so all I have done was:

node (D7) -> node (D8)

select nid,vid, 'article', UUID(), language
from node
where type = 'story'

field_data_body (D7) -> node_body (D8)

select 'article', null, entity_id, revision_id, language, 0, body_value, body_summary, 'basic_html'
from field_data_body
where bundle = 'story'

node (D7) -> node_field_data (D8)

select nid, vid, 'article', language, status, title, uid, created, changed, promote, sticky, 1, 1
from node
where type='story'

node (D7) -> node_revision (D8)

select nid, vid, language, created, uid, null, 1
from node
where type='story'


node (D7) -> node_field_revision (D8)

select nid, vid, language, status, title, uid, created, changed, promote, sticky, null, language
from node
where type='story'

Of course, these are just simple queries for just one particular article type without any additional fields, but the point was to show which tables need to be updated to at least get the content in the Drupal 8. Other (field) tables will require more sophisticated SQL exports.