While they have stop Den-O ages ago, they still try to rehash elements of Den-O after 2007. I feel like Den-O help inspire the goofy main Rider and serious secondary Rider, nonhuman partner who directly helps the Rider fight and extremely over-the-top comic relief that we have gotten in the last 8 or 7 years.
Heisei Rider has always had the "goofy main Rider/serious secondary Rider" dynamic, though: Shouichi and Hikawa, Shinji and Ren, Hajime and Kenzaki. Godai and Ichijou have the personality dynamic even though Ichijou isn't a Rider (and in any other series, he would have been the secondary.) Even Kabuto did it - although Kagami is a nicer person than Tendou, he takes things much more seriously, while Tendou is OTT. Conversely, at least four shows since Den-O didn't do this (Decade, OOO, Wizard and Drive.)
W is arguably just as much to blame for the "non-human partner" thing; it was so successful that Toei repeated a variant of the Philip plot for three subsequent years in a row! And as you pointed out, Den-O was a long time ago now - Toei's a business, they have to go with what sells. They're not going to just blindly copy an old show for the sake of it. If the comedy was harming the shows' commercial performance, or kids didn't like it, they'd change it. Like how they did Gaim as a complete change from the format of the last four years, or how they tried to overhaul Sentai with Go-Busters (which, until the poor sales and ratings started to bite, had noticeably much less comedy and slapstick in the early episodes)