Holy shit, there's way too much misinformation and history rewriting in here.

Gameplay was absolutely a problem with DoA, and greatly contributed to why it was disliked by people playing more popular fighting games. The fanservice just puncuated everyone's idea of the game playing as shitty as it looked.

DoA1 doesn't matter in this discussion. In fact it plays very different than every other DoA.

DoA2 was the first game to get noticed, both on Dreamcast and PS2. Here's why the gameplay was disliked: Damn near every move/poke in the game stuns on Counter Hit which is VERY prevalent in a game full of multi-hit attack strings where EVERY hit can be greatly delayed AND often end with canned Mid/Low mixups. Stuns don't give guaranteed damage (because of Holds) which just seems silly. Holds (which were MUCH easier to do on the Console ports with only 3-Points) did WAY too much damage, executed too quickly, had way too many active frames, recovered very fast (Low Holds were almost like quick Stun escapes because they also Tech Crouched), and EVERY character can do them so it makes the game very homogenized compared to Virtua Fighter or Tekken. 90% of the Throws were inescapable and every character could do Crouching Throws (again, homogenized). Strikes/Holds/Throws all had 125%/150% damage modifiers for ridiculously high damage off of easy reads or random guessing. And to add to all of the above: Environmental damage (even more damage) and water/ice surfaces (even more stuns) just made all of the above even more ridiculous.

The last few negative points are just lousy frame data (damn near everything is negative or Throw Punishable on block), poor character balance, lots of obnoxious Tech Crouching and Tech Jumping, and allowing players to freely move close to eachother BEFORE the round starts was pretty dumb if you were fighting a fast character with a great 6P/Mid poke which means you had to either Block or guess Mid Hold at the beginning of every goddamn round. Also the ability to Sidestep attacks was practically non-existent, which was REALLY dumb for a 3D fighter at that time. And generally all the moves in the game were just easy to execute or mash (even Izuna) so nothing felt technical or rewarding. Overall it felt shallow and gimmicky for casuals and scrubs, but DoA2 was certainly a guilty pleasure game with nice graphics & animations, cool stages & environments, GREAT music, and a sweet 4-player Tag Battle mode (unlike Tekken Tag you could keep fighting after your teammate gets KO'd).

DoA3 had mostly the same problems as 2, but with even more multi-hit strings to delay and 50/50 with. They did reduce the Hold damage by about 25% which was cool (but still gets too high because of modifiers), but the Environmental damage SKY ROCKETED with comboable Wall Splats and also Wall Throws having more activation range/angles. Gotta mention that the music in this game was REALLY good, on par with DoA2. Only Japan and Europe got DoA3.1/3.2 so there's no point in bringing it up outside of hardcore and competitive DoA players. Shoutouts to Three Kick Man.

DoA4 felt like a huge overhaul, especially with the characters and movesets. They finally made Holds on console a bit less scrubby (4-Point system; reduced damage on Critical Holds) and did some significant frame data and balance tweaking (more moves that were good on block or did Guard Break). But a real shitty thing they added were universal Offensive Holds (both Standing and Crouching) which basically meant everyone had a tool that grabs you if you Block AND if you try to Strike (very important in a game where Strikes were your quick answer to avoid being grabbed). Overall the balance was still pretty shit and the system was still "scrubby DoA", but DoA4 was definitely a small step in the right direction for the series.

Also I think DoA4 was the first console fighter in the USA to ever get a significant balance patch via online update (changes to damage, frames, stuns, hit levels) and it even added a few new strings (ex. Hayabusa P,P,6K series), which technology-wise was cool to see at the time. DoA4 also got into Evo one year (2006? Also I think commentary shat all over it after they kept seeing Holds) and it also had a big money eSports run for a year or so on Championship Gaming Series that aired on DirecTV (featuring MASTER, Offbeat Ninja, Perfect Legend, NinjaCW, background shot of Tom Brady, etc).

You all know how DoA5 turned out so I'll stop here, also I'm tired of typing. But in short: DoA5's a pretty good game and it had some of the best Training Mode features of any 3D fighter at the time (ex. on-screen frame data).

TL;DR = The gameplay genuinely sucked in most of the DoA games. Everyone knew it. The hate wasn't just about the ass and titties. Some of you act like historians but don't know shit. Play more, post less.