Are you trying to tell me that I can't make my 1000 mile-long super-duper hyperdreadnought carrier (equipped with two million laser batteries and mass drivers, five hundred thousand missile pods, ten Death Star-style hyperlasers, and entire squadrons of capital ships it deploys like they were fighters) capable of slipping past enemy radar until it's physically poking their sensors? Because I'll have you know that I won't let realism ruin my wanki-I mean, fun.
But yeah, I generally try to be as realistic as I possibly can without devolving into arbitrary number crunching. Never planned on having stealth ships in space (except for fighters and lightweight special operations corvettes), never do.
I wouldn't say a cloaking device in space is so much unrealistic as it is pointless, because almost all spatial engagements between large fleets should be non-LoS anyway. Other methods of hiding a ship, such as RADAR-absorbent paint and signal-masking, could still work.
This shouldn't be too much of a problem for me anyway, since neither Mecharussian nor FTMekh space warfare doctrine relies upon stealth too much.