No matter what you do, you're going to have to do a lot of work. Going forward, Drupal has changed the way major upgrades are done so from now on instead of major efforts to go from D5 to D6 to D7 etc. there should be only a small amount of ongoing work necessary to keep your site up-to-date. But you have to get to at least D8 to take advantage of that ...
Using Migrate to go from Drupal 6 to Drupal 8/9 is pretty well documented, and the problems you will encounter are mostly known and also documented. But this Migrate process doesn't work for Drupal 5, so I suggest trying to update from D5 to D6 first. This is also a pretty simple process. See for example Upgrading from Drupal 5.x to Drupal 6.x - Tutorial
How well this all works out will depend on a lot of things specific to your site, mostly whether the contributed modules you rely on have been ported to D6/D9 and whether they support Migrate for going from D6 to D9. Another problem is going to be your theme - theming has changed substantially between D5 and D9 so you might have to do a lot of work to get the look you want. You will not be able to keep the same look as you have now, but that's probably a good thing because D5 sites look really dated.
If your main goal is to preserve your content, then I think your chances of success are much better if you stay with Drupal than if you try to move to some other CMS / software because even though D9 is quite different from D5, the jump is less than the difference between Drupal and WordPress.
