Teams routinely use an extra DB anyway, so adding a WR and using a TE doesn't change that anyway. 70% of the Cowboys defensive snaps the last several years they only used 2 LBs and an extra DB.
You still don't seem to get that there is more to offensive football than having the fastest guys on the field. There is a system where, if things are coached right, everything syncs together with all the roles players are filling. It's much more intricate and detailed than just sending the fast guys out on routes. Aside from run blocking, TE's can also help with pass blocking - Steele would have had a much harder time against Bosa without some TE help. Even if not staying in to pass block, they can get a chip on the DE before running a route. A great ploy all teams use is having the TE chip then run go into his route after all the DB's have cleared out chasing the outside receivers … double benefit in slowing the pass rush and providing an extra receiver. And, clearly you miss the fact that sometimes we do use 4 WR's - when we go with an empty backfield. That provides 5 receiving options with the TE.
End of the day, sorry bud, the TE's are producing, the offense is rolling, and you do not know more than Kellen Moore, Mike McCarthy, and O-Coordinators all over the NFL.