The thing that makes RC a large cut above almost all other popamole shootaz in my view is that it's much more than just 'press f to pay respects'. It's not all that much style over substance - sure, the levels are rather tight, it's linear to boot, etc, but the gameplay itself is still gripping and satisfying.
It has many setpieces that are just
tremendously well-done. All those last stands, assaults, races against time when planting explosives, etc, are not only very cool in terms of presentation, but they are also fucking hard and not only do they require you to position the other commandos optimally in special spots, but you also have to use your guns properly. If you can't hit shit with the sniper rifle while you are being swarmed by the geonosian elites, you're boned. I always get all tingly each time I remember the derelict ship hangar defences and assaults, reclaiming the ammo crates section on Kashyyyk, the final showdown on Geonosis where you have to reclaim data from a minute-long terminal slice while super battle droids storm you from two sides. It's fun, it's gripping and it's tough, and you often find yourself boned the moment you get incapacitated, because your other bros are kind of shit at doing stuff themselves. But similarly, if one of the dudes mounting an anti-armour position drops, you're also in big trubble.
I also disagree that around the midgame it gets boring. The only thing that is introduced on Kashyyyk are the cyborg bodyguards, yeah, but the entire chapter is p. much the apex of the entire game. You face the most overwhelming odds there, it's the toughest in terms of setpieces, you have to act quickly, and you have to act smart.
And finally, to come back yet again to 'press f to pay respects', what RC does considerably better than all other shooters like this, is that it gives you the best illusion of actually being in control. It never tells you to get around a locked door. There's never a chest-high wall blocking your way. You never have to encircle an MG42. It's always "let's rearrange some architecture, commandos", "set up sniping position, delta" and "mount that turret!". That is also further supplemented by most of the setpieces having destructible terrain that you can use to crush droid dispensers, unlock new manoeuvres, etc, and some of them aren't even that obvious.
Republic Commando is very dear to me for two reasons. One is that I think it really nails down the 'commando' aspect of getting in more or less quietly, blowing everything to hell and exfiling before they know what hit them. In this regard, it's similar in style to the Crusader series, and I've always been reminded of it when playing RC. Second is that I've always, always wanted to play an SW game where you get to play a stormtrooper. The closest I could ever get in that regard was TIE Fighter, and obviously that's not very close to home, isn't it. Republic Commando kind of does that. Of course, Imperial Commando would be my wet dream, but LUCASAAAAAAAAAAAAAAAAAAAAAAAAAAAAARTS