MySql not using an index

DB engine is MySql 8.
I am running a simple query on a table that has an index on id column however its not using the index and its doing a full table scan.

The table has statistics updated the column of id is int and the index is also on int.

I dont want to change the query and use force index and in Maria db it is using the index correctly.

Here is the explain plan:

1	SIMPLE	user_actions		ALL	index_id				558242932	0.0	Using where; Using parallel query (2 columns, 1 filters, 1 exprs; 0 extra)
1	SIMPLE	user_actions		eq_ref	PRIMARY	PRIMARY	8	db.user_actions.id	1	100.0	

I have gathered stats and expected that the optimizer will use the index while the where clause is filtering by this column using " id in (3,5,7,34,56)

You never included your actual SQL query, but for the purpose of this answer, I will assume your query looks something like:

<!-- language: sql -->

SELECT *
FROM yourTable
WHERE id IN (3, 5, 7, 34, 56);

This is the same as:

<!-- language: sql -->

SELECT *
FROM yourTable
WHERE id = 3 OR id = 5 OR id = 7 OR id = 34 OR id = 56;

Queries with OR conditions in the WHERE clause are hard to make amenable to index use. Such a query will probably not use an index on id, because doing so would either require several index seeks for each value, or a single full index scan. In either case, MySQL might just decide to scan the entire table, which is what your query plan seems to be saying.