Travel Agents are still a thing, although there are quite a lot fewer of them than there were in the 90's.
If you know where you are going, where you are staying, when, how, etc then you can pretty much do all that yourself online, no need for an agent [1].
But if you want advice, then agents can be useful. Say for example I want to visit Barcelona, a place I've never been. An agent can help me plan that (when to go, where to stay, what can/should I do etc.) They're like an intelligent Google. They'll also likely know some hacks to make it cheaper if I'm flexible enough. They can do a lot more than just purchase tickets for me.
[1] I needed an agent once. I was flying from the UK to USA on United. I live (and my CC is based in a country United doesn't fly to directly.) United _requires_ me to use the "web site of the country matching my credit card". Except they don't fly to my country, so no web site. I could book online, but no way to complete the purchase. I ended up using a travel agent in London (which is where I _was_) to make the booking for me...
If you know where you are going, where you are staying, when, how, etc then you can pretty much do all that yourself online, no need for an agent [1].
But if you want advice, then agents can be useful. Say for example I want to visit Barcelona, a place I've never been. An agent can help me plan that (when to go, where to stay, what can/should I do etc.) They're like an intelligent Google. They'll also likely know some hacks to make it cheaper if I'm flexible enough. They can do a lot more than just purchase tickets for me.
[1] I needed an agent once. I was flying from the UK to USA on United. I live (and my CC is based in a country United doesn't fly to directly.) United _requires_ me to use the "web site of the country matching my credit card". Except they don't fly to my country, so no web site. I could book online, but no way to complete the purchase. I ended up using a travel agent in London (which is where I _was_) to make the booking for me...