If you have to raise your seat by changing the seatpost, then the handlebar stem is probably too short too. That would be a typical shortcoming.

That is, you can use a longer seat post, raise the seat, and find that even with the stem maxed out, the handlebars are still too low.

In most cases, you want the seat to be about level with the handlebars.

If you are replacing the seat-post, check the stem too just to be sure.