Previous owner rigged up the weirdest bathroom fan solution

I've been in my house about 8 months now and just finally got around to investigating why my master bathroom has this janky looking setup. The bathroom fan was making this god awful rattling noise since day one but it actually vented really well so I kept putting it off.

Went up in the attic yesterday to finally replace the whole unit and turns out the previous owner didnt even have a real bathroom fan installed. They took an old computer case fan, wired it into a regular light switch, and duct taped it (yes duct tape) to a 4 inch dryer vent that goes outside. The whole thing probably cost them like $15 and some spare wire they had laying around.

I was gonna rip it out and install a proper Broan fan but decided to test it with some steam from the shower first. This stupid computer fan cleared the mirror fog in like 90 seconds. I looked up the actual bathroom fans at Home Depot and theyre going for $80-150 depending on CFM rating and mine would need the 110 CFM one.

Now im sitting here wondering if I should just secure it better, maybe swap the duct tape for some proper HVAC tape and call it a day. I already have money set aside for a proper fan but kinda wanna see how long this thing actually lasts before I replace it. Part of me feels like I should do it "right" but the enginerd part of me is like this is actually pretty clever lol