I am curious to know how relevant is the firewall service today. I am very interested to hear your opinion, and also what type it can be (hardware or software)?
Still super relevant, especially with how often sites get poked at these days. Both hardware and software firewalls have their place; hardware's great at the edge, but software firewalls give you more control right at the server level.
Very relevant, you should have minimum (3), between your clients (in case of infected client with malware), in front of the internet (classic), and on the carrier in form of Gre tunnel ddos protection, inline protection from carrier, or blackhole /32 announcement.
Depending the firewalls can be software based or actual physical firewall device. I prefer actual firewall device. It gives you the autonomy to control that firewall as you see fit.