So will AITA if I don’t tip? Is it really my personal responsibility to make sure my server is paid enough?

ABSOLUTELY NOT Don't let anybody tell you otherwise. It is and should be employers job to pay their workers a living wage in a rich country not the buyers.

Culturally, there will be people who will look down on or say nasty things to you if they find out you do not/did not tip. This happened to me. Some of the nasty comments (these are not said by the employees) people say are "The employees will remember this and may spit in your food or tamper with it in some way next time you order, which has got to be illegal for health code reasons for employees to do and is guilt tripping on the person who says this comment. Not only that, but those who say such awful things are continuing the nasty treatment of employees by the ruling class by saying such nasty remarks.

Others have answered the question, but I did want to mention - many people mention that tips are important because employees can be paid below minimum wage, but this varies state by state, and in my experience tipping is standard regardless of this.

Here's a table of minimum wage by state:

https://www.dol.gov/agencies/whd/state/minimum-wage/tipped

The "Minimum Cash Wage" column is the "tipped" minimum wage - this is what employers can pay for jobs that get tips. The "Basic Combined Cash & Tip Minimum Wage Rate" is the minimum wage for non-tipped jobs, as well as the minimum a tipped employee must receive in wage plus tips - if they don't make enough tips, legally the employer must pay the difference.

So for example, in Washington state where I am, the minimum wage is $15.74 whether you're tipped or not, but it's still considered rude not to tip, and 20% is still the standard "good" tip.

Tipping culture used to be a courtesy, but now it’s been classified as part of salary so restaurants don’t have to pay minimum wage to their waitstaff. You’re not required by law to tip, but depending on the place, waitstaff will remember if you tip or not and how much.

Tipping has not gone away except in some places where they explicitly say it’s not necessary.

Typically I double the tax amount and leave that as the tip. I will also round up from there if it’s an uneven amount to reduce change. Finally, I’ll pay more if service is exceptional or I’m being served by someone I know personally or if they’re doing me a favor.

Some places include tips in the bill, so be careful. I also usually don’t tip if picking up food because there is usually no guarantee that my tip would actually go to the people who actually prepared my order.

I also tip other service jobs (Barbers, mechanics, plumbers, etc..)

Only tip your server at restaurants and food delivery people, anywhere else is a scam. Servers and delivery people can be legally paid way less because they're expected to live on tips, its shit but its how it works. If you don't tip them they could have basically worked for you for as little as 4$ an hour. If you're worried about amounts, just go for 15%, its the expected amount. Skip if they suck at their job though.